The Free Application for Student Aid (FAFSA) is a request for federal financial aid in the United States. Upon completing the FAFSA, the student becomes a candidate for several federal programs, including the Pell Grant. While not all students will meet the requirements of FAFSA -- the program is based mainly on students' financial need -- many other scholarship programs require students to complete the FAFSA first. In fact, some private organizations require students to be rejected for federal aid before they will consider them for a scholarship.
Filling out the FAFSA can be confusing. You'll need your most recent tax information. If you're a dependent, you'll need the assistance of your parent or guardian while filling out the form. You'll also want to be sure your form is free of errors before you submit it. It's best for high school students to file their forms during their senior year as close to January 1st as possible. But don't sign or send the form before that date.
One thing to keep in mind is that you'll need to reapply for the FAFSA each year you're in school or as long as you want to remain eligible for aid. The federal government has a renewal form that isn't quite as extensive as the initial form.