The reinstatement is an application that will be submitted to USCIS to request them to reinstate your student visa status if you have a terminated SEVIS record. Reinstatements are only filed if you choose to remain in the U.S. to continue your studies with a terminated SEVIS record.
If USCIS approves the reinstatement request, the adjudicating officer will endorse your I-20 to indicate that you have been reinstated and will return the I-20 to you. If USCIS does not approve the reinstatement request, you may not appeal the decision and need to prepare to leave the U.S. immediately.