In short, you just teach about whatever topic they provide to you (or if you're lucky enough to choose your own, a topic that you are overwhelmingly comfortable teaching about) in a fashion that demonstrates your teaching style (e.g., lecture delivery, use of in-class exercises/activites, student involvement, powerpoint usage or lack thereof). They just want to see what you are like in the classroom, especially how you interact with the students. Prepare a really "killer" lecture that involves the students and practice, practice, practice. Do that and you should be good. Good luck.
P.S. As someone who went to a major R1 and is in their first year at a SLAC, I hope you like to teach. A lot ;) And I hope you like SLAC undergraduates (who expect a lot more from their professors than typical R1 undergraduates, at least in my experience).