College applications question...

As a high school junior, I hear a lot about the college applications process from friends, but I know very little about it. So I have a curious question:
I have done alot of research about the common app and even made an account just to check things out. But I know that in addition to the common app, many schools require a supplemental application. What does this supplemental application normally contain? Is it just additional essay prompts? Does it require more specific info about grades/EC/awards/test scores/ect.?

Thanks!

To answer your questions, it is best to look at the specific college websites and see the requirements for Freshman admission. If supplements and additional information are required, it should be spelled out on these websites.

If you made an account, add a few schools to see. It varies. Some require nothing more, others require essays, more questions, etc.