If you drop all of your class(es) by the session's posted last day to drop with a 100% refund, your financial aid awards will be removed from your account and you will not be responsible for any student loans that were accepted, and you will not receive any grant or loan funding. Check the Academic Calendar for your session's last day to drop with a 100% refund.
If you drop your class(es) after the posted last day to drop with 100% refund, it is considered a withdraw and you may end up owing a portion of the financial aid received for tuition. This only happens if you withdraw from a class and/or fail all classes in a given semester. This is called Return to Title IV (R2T4). The amount owed will be calculated after all final grades have been posted for the semester.