Colleges offer a 4-year Bachelor's degree and beyond (like medical school, law school, grad school, PhD, etc) that you'll need for jobs like lawyer, scientist, doctor, nurse, therapist, social worker, pharmacist, etc. Most students live on campus in dorms, eat in dining halls, belong to fun student organization, and go to athletic events.
Colleges have minimum GPA & SAT score requirements in order to admit you and they'll award grants and scholarships based on your grades.
Colleges could either be private or public. Private schools generally have a higher sticker price, but are able to give out more financial aid.
In college, you pick a major that will correspond to the career field you want to enter. (example, future therapists student psychology. Future teachers study education) and then you complete all of the required courses for that major to earn your degree.
College offer some various majors so explore the website of colleges and make sure they have something that interests you and apply online the fall of your senior year of high school.
Sometimes colleges require an application fee, but if you have financial need you may be eligible for a fee waiver so you should speak to your college adviser.