Everything You Want to Know About FERS Federal Retirement (OPM.gov)
Article Excerpt: "...FERS is a retirement plan that provides benefits from three different sources: a Basic Benefit Plan, Social Security and the Thrift Savings Plan (TSP). Two of the three parts of FERS (Social Security and the TSP) can go with you to your next job if you leave the Federal Government before retirement. The Basic Benefit and Social Security parts of FERS require you to pay your share each pay period. Your agency withholds the cost of the Basic Benefit and Social Security from your pay as payroll deductions. Your agency pays its part too. Then, after you retire, you receive annuity payments each month for the rest of your life...."
Resource: www.opm.gov