1. CSS Profile
About 300 colleges (mostly private, but a few public universities as well) require the CSS Profile to be completed for families applying for financial aid
When the Profile is required, it is always in addition to the FAFSA
Colleges use it to determine eligibility for institutional need-based aid, in addition to federal aid

2. CSS Profile continued
The Profile is administered by the College Board.
Colleges that use the Profile will indicate this on their websites, and provide a link to the Profile website:

3. Differences between the Profile & FAFSA
Submission dates- Profile can be submitted in the fall; the FAFSA not before January 1.
Questions specific to each school
Different methodology (Profile factors in if you own your own home for instance). In general, the Profile is more detailed.
Profile requires a minimum student contribution
Greater reliance on professional judgment
Cost- Profile has a per-school fee ($25 for the first school, then $16). Fee waivers are available, and distributed automatically for eligible families.
(source-

4. Completing the PROFILE financial aid application
Your first step is to register for the PROFILE.
Once you are registered, you'll be able to complete the PROFILE application (either the online version or the paper form). Some schools may require you to complete additional forms, such as the Business/Farm Supplement or the Noncustodial Parent's Supplement.
Gather all the material you’ll need to answer the questions. For example, you will have to know the amounts for salary, dividend, and interest income; taxes paid; and the value of any savings and investments.
After completing the application, you'll receive an acknowledgement summarizing your PROFILE information and listing your colleges.
(source: Peterson’s College Guidebook)