Michael (my brother, for those of you who haven't yet caught on) brought up a question in the comments on the previous post: what do you do, anyway? Kid brother knows that I'm a professor, and that that includes both teaching and research. But the kind of teaching that we do here is different than what he's training to do (4th grade). So even though most of my readers are academics, I thought I'd answer his question in blogular format. Commentariat, feel free to modify this as necessary.
For those at the college/university level in general, the "teaching" part of our job (which is generally 40-60% of our workload overall) consists of three main thngs: 1) course development and preparation; 2) delivery; and 3) evaluation.
Course development and preparation is just that. First, you come up with an idea for a course. Some of this may be preset for you: for example, my Western Civ. course was already in the catalog when I was hired. On the other hand, you may propose entirely new courses based on your own interests: gender, or monasticism, or Tudor-Stuart England, or whatever. The balance between these two varies widely from one university to the next. But whether it's an old course or a new one, you need to come up with your own syllabus (that is, the order of lectures, discussions, and assignments), determine which books will be assigned, order them, panic when the bookstore forgets two of your five texts… Oh, and write lectures and plan discussions. In general, we have much more freedom in course development than K-12 teachers.
Delivery: Get up in front of a class and lecture. Don't choke, or at least don't do it during the first two weeks. In my opinion (and some may disagree), lecturing is relatively easy. It's leading discussions that's hard. When I lecture, I have more or less complete control of what's going to happen. When I lead a discussion, there's a chance that many of the students won't have read, or will be too shy to speak up even if they had – there are any number of things that can go wrong that I can't control for. In any case, depending on your institution, you will be teaching anywhere from two to five courses a semester (though some of those may be repeats). I generally teach three courses a semester, all different, but some of which I will have taught in previous semesters. This means that I have the choice to recycle some, all, or none of my lectures from one year to the next. I generally go with the "some" option, to keep myself from getting stale, without overworking myself. (The jokes, however, are all of ancient vintage.)
Evaluation: Grading. And grading. Only in rare cases will a class in the humanities have a multiple-choice test as an assignment. We are heavily writing-based, which means that grading takes a long time. It's my least favorite part of the job. It's also the part that takes the longest, both in the doing, and in the dealing with student angst afterwards. I'm fair, but I'm pretty tough.
But brother dear, shall I tell you my absolute favoritest reason to be teaching at a university, rather than at the K-12 level? It's not the pay: in many places, high school teachers make more money than professors, and without the obligation to spend summers researching and writing. It's simple: FERPA. More precisely, a small codicil in the Buckley Amendment to the Family Educational Rights and Privacy Act that says that, once a student is 18, their educators are forbidden to discuss any matter of the student's schoolwork or grades with anyone else without that student's written permission. FERPA : helicopter parents :: garlic : vampires. You will understand this once you start teaching in your own classroom.
Good luck, kiddo.