Some job announcements may say "This is a bargaining unit position". A bargaining unit position is a job that is represented by a labor union. Bargaining units cover more than half of the jobs in the Federal Government. Labor unions negotiate various conditions of employment for these jobs; however they don't generally negotiate compensation or other matters that the management team deems to be their sole prerogative.
If your job is in a bargaining unit, you don't have to join the union. However, if you want to join a union, your job must be in a recognized bargaining unit.
Appeal rights
Typically, you need to be in a bargaining unit job if you want to file a complaint using the negotiated grievance procedure.
Each union has their own grievance procedures which you can find in your Union Handbook. All union members, whether you're a paying member or not, have access to appeal rights and grievance procedures, including the EEO complaint process. If you're a union member you also have the right to union representation in all grievance procedures.
For more information on your appeal rights please refer to a copy of your Union Handbook or ask your HR department if you don't have a copy.