TL,DR: It's varied and requires a lot of different skills that I didn't learn in school.I get to work on what I want to work on. I get to choose my own hours. But there are a lot of responsibilities beyond simply doing research and teaching. What these are depends on the University and field of study.My life as a junior professor at Stanford (up for tenure in the fall) consists of the following.TenureStanford is a research university. All tenure decisions are based off your research reputation in your respective community. You have to be competent in the classroom, reasonably collegial to your colleagues, but in the end the cliche of "publish or perish" is true.Tenure is an up-or-down decision. You get it and you have a job for life or you don't and you must move after the following year (i.e. you're fired). Stanford's tenure system is a real review - they go out for 15 to 20 unsolicited letters to senior members of your community (i.e. you don't get to pick the writers) and these letters ask about your standing in the community and if you're up to Stanford's standard. Based upon how those letters come back, this will determine if you're fired or not. You never get to see the letters or respond to them.ResearchSo life as a junior (untenured) professor is really trying to build a record that will get you tenure. If you see young professors looking tired and stressed, that's why.Writing research papers to be first published on preprint servers (see http://arxiv.org ) and then in proper journals is a major component is the primary product of research. What goes into that research obviously varies a lot by field. Since I'm a theoretical physicist, there are a lot of pen & paper calculations, numerical calculations with Mathematica, and numerical Monte Carlo calculations (these last ones produce huge amounts of data and is why you'll see me asking lots of programming questions).There's a lot of variation in the rate people publish. I tend to be between 6 to 10 articles per year. Most research projects take between 6 and 12 months to finish, so I tend to have 4 to 6 projects going at once. Making them all move forward smoothly is a major challenge. I tend to spend more time editing papers than doing calculations now. I don't think I would have thought that when I was in school and eschewed English courses.When you submit a paper to journal, it gets sent out to be refereed (i.e. reviewed for quality). This can be trivial or a pain depending on the situation. Sometimes, the anonymous referee rubber stamps a paper, other times, they give valuable feedback, and frequently they give their own opinion. Recently, I had 3 month battle with a referee over frequentist vs Bayesian statistics. I eventually got frustrated and sent it off to another journal (equally prestigious) which accepted the paper without complaints.You also have to be a referee. The general rule of thumb is to wait for one or two rounds of harassment before you respond, otherwise you'll get more and more reviews to do.Ultimately the research is evaluated by overall impact which is measured through the above letters and through the more objective (though overly simplistic) citation count (see http://inspirehep.net ).TravelOne major component for building an international reputation in my field is traveling. You travel to give seminars and colloquium and also go to conferences and workshops. I spend about 3 - 4 months a year traveling on a shoe-string budget. I'm about to hit 1M miles on American Airlines.On any given day I may fly into London, go to Oxford to give a seminar, then fly to CERN (in Geneva) for a meeting, drive to the Alps for a workshop and then fly to a summer school in Italy and be home in a week to 10 days. Repeat several times a year. It was glamorous when I was going to places for the first time, but most places I've been to multiple times and it all blends together.I carry my passport and 5 currencies (USD, JPY, EUR, CHF, GBP) on me at all times as well as a filled up CharlieCard, OysterCard and MetroCard -- this is so that if I forget about an international flight, I can go directly to the airport and buy clothes and toiletries when I arrive.I pack for a 3 week trip in under 30 minutes and only use a carryon.I often don't remember which flight I booked until I check the night before -- simply can't fill my brain with non-urgent information.My Facebook feed is filled with 3 letter IATA codes to let people know where I am.This isn't to brag, but to demonstrate how draining/disheveling building/maintaining an international reputation can be.Public SpeakingPublic speaking is huge factor. Giving concise, entertaining presentations is important. I spend a lot of time editing Keynote presentations. I tend to give about 20 hour-long presentations per year on recent research projects and another 5-10 special topic presentations. I spend a lot of time making figures and simplifying the research to make the work presentable. Summarizing your work well in person is one of the key components to getting more citations. As a kid, I would have never thought I would spend so much time speaking before audiences, but I've really grown to enjoy it.GrantsGetting money is a big factor in tenure. So you apply for a lot of grants. Government grants are typically 30 to 50 page applications filled with budgets, descriptions of research, etc. You have to follow the rules to a T -- think of it as filling out your taxes -- the language is obtuse and confusing and not getting a specific grant could sink your career or cause you to lay off staff. Grant applications usually take 100 to 200 hours the first time you apply and then 50 to 100 hours the next time. They're due at random times during the year and you typically have 6 weeks notice to fill them out. I don't know anyone who likes filling out grants, but when you get one, you're on a high for a week.Mentorship and Personnel ManagementYour research is the raison d'etre for your position at most professors in the sciences at research universities. So you have to be performing research constantly. Most people develop a team around them consisting of graduate students, postdoctoral researchers, technical staff (all of whom you're paying off of the grants you've received). Depending on the funding situation, you could have 1 to 2 people up to 20 (if you're very well funded). This means that you're a manager now. You're also a mentor for these junior colleagues.This aspect of the job requires a lot of hiring. When positions for postdoctoral positions become available, we get 400-600 applications and we're filling 1 to 3 positions. You have to read and scan through applications. Postdoctoral positions are very expensive when you include overhead and typical 3 year position runs between $300k to $500k, so postdoctoral hiring is taken very seriously.Letter WritingIn order to get the best people you have to develop the existing researchers -- which means getting them jobs. So you have to spend a lot of time writing letters of recommendation (usually in the fall). I currently write about 15 to 20 letters per year in a matter of 3 months. These letters are scrutinized and if you say the wrong word it can cost them the possibility of getting faculty positions (thereby destroying your ability to hire the best people in the future).Graduate Student MentorshipGraduate student researchers are important for most professors' research. You have to bring them from knowing next-to-nothing to being independent researchers over 3 years. This requires a lot of mentorship. Graduate students are pretty young and need to develop their philosophy of research. This means a lot of long conversations usually. Many are foreign and so there are frequently cultural issues and language is frequently below-par and has to be improved.Graduate students typically aren't very professional when they start and you have to deal with their individual quirks in delicate ways. You have to tailor projects to their abilities and find out how much they can do before they become overwhelmed. You have to lift them up when they hit a wall and don't feel like they can go on (it happens to every graduate student at some point and frequently multiple points). You have to keep them excited when they get burnt out on a project even though they're only halfway through it and they don't necessarily see the point.Most graduate students get livable stipends these days ($35k at Stanford). That means more grant money. At Stanford we have to pay for their tuition for 4 years which brings a fully loaded student up to $80k/year.It's funny the types of things you have to teach students:I gave driving lessons to one (it would have eliminated a sizable fraction of their post-doctoral opportunities)Taught programming to severalTaught statistics to all the studentsEducating graduate students really is a multi-faceted apprenticeship program.Local / National / International Committee WorkThere are also committee work and meetings to do. Once you become faculty, you are a manager of the department and wider university. You have faculty meetings, committee meetings, etc. I'm on a few fellowship selection committees (both local and for the US government). I also am on the graduate admissions committee frequently (a major time-sink in January). I've been in charge of space renovations on my floor. I'm also a pre-major advisor this year. There are also faculty hiring committees which are very political and can drain a huge amount of time.As faculty you also become a member of the national / international community in your respective fields and are called upon to be part of panels and reviews. The longer you go, the more you get called upon.(I just got reminded by a foreign funding agency that I'm late in turning in a grant review.)Other Academic ActivitiesOne aspect of an active academic environment is seminars. In my specific subfield, there are 4-hour-long seminars per week on average. There are another 3 relevant hour-long seminars I sometimes attend. There are additionally 2-hour-long colloquia per week. I usually attend 2 to 3 hours of these per week.The speakers at the seminars and colloquia have to be entertained and so there are a lot of dinners that I have to go to. At one point, I'd been to almost every restaurant in Palo Alto. By in large these are relatively enjoyable, but there is such a thing as too much of a good thing.TeachingFinally, there is teaching. I teach one to two quarters per year. I've taught a mixture of graduate and undergraduate classes. Teaching is fun and I think a fair fraction of faculty would love it, but the limited time available to prepare a course really prevents most of us from spending as much time as we would like on it. I find it fulfilling to be up in front of the classroom, writing lectures and designing problem sets, but unfortunately, I only can put in 10 - 15 hours per week into a course.