You attend college like anyone else for the most part. You typically have one military class in your schedule, and a few non-academic activities to participate in. I think you might wear a uniform one day a week?

You spend a month or two doing a variety of training during the summer, some of which can be a lot of fun.

If you are not a scholarship student, you may be offered a commission upon graduation if they need extra bodies and you did well enough.

If you are on scholarship, you will have committed service after graduation. You can get a 4 year scholarship prior to college, but if you don't have one you can just show up and participate in ROTC and they will likely give you a scholarship for the last 2-3 years of school if you do well (in ROTC and academics). This allows you to try them out and vice versa.

The commitment varies depending on service branch and what specialty you end up doing once commissioned. Not sure if the shorter scholarships have a shorter commitment?