FERPA is a United States law that protects the privacy of a student’s academic records. You have to allow your school to send the information to the colleges you apply to and there is a spot in the common application for this. This also authorizes the schools to talk to the college if they call for more information about you.
The second part to FERPA and college admissions is a bit more confusing. Under FERPA, you have the right to see anything submitted to schools on your behalf after the application cycle is over. The application has a spot for you to waive this right. The reason being that this way teachers can feel free to write whatever they want on the recommendation letter, without fear that you will see it later. It is usually recommended that you waive your rights, because if you do not, some teachers will not write a letter.