Grants are generally need based and do not have to be paid back. One type of this aid is a "Pell Grant," a need-based grant that is federally funded.
Scholarships
These are usually based on academic, athletic, or artistic achievments. They are not necessarily need based. Scholarships can be public or private and, can also be exclusive (meaning only certain people may apply), or open (meaning anyone may apply).
Work Study
Work study is a program where a student takes on a part time job sponsored by the school, not more than 20 hours per week, and are paid on an hourly basis.
Fellowships
Fellowships are similar to work study, but placement is in a field of study related to what the student's major is in.
Loans are not need based and can be paid back while in school, or deferred until six months after a student is no longer enrolled. Anyone who is matriculated and taking at least six credits per semester can receive a loan. However, if you have ever defaulted on a student loan or owe a pell overpayment, then you will be denied until your situation is resolved.
General Tips
It is always good practice to inquire into each school, and even each major department, to see if there are scholarships or other aid available.
Go online or to your public library to do research about available aid as well. Millions of dollars go unclaimed each year, simply because people aren't doing the necessary leg work to find it. Optimally, you began researching at least a year in advance of enrolling, but it is never too late to start.
