As an adult you should get a TDaP vaccine once every 10 years. For women who just had a baby you should have a TDaP vaccine, along with their spouse. Children will get their TDaP vaccine at 2 months, 4 months, 6 months, 15-18 months, and again at 4-6 years. Some schools now require it before entering the 7th grade to protect against whooping cough. http://www.cdc.gov/vaccines/pubs/vis/downloads/vis-dtap.pdf
Tdap is shorthand for tetanus. It is a shot to help prevent against the disease tetanus that can cause lockjaw and against a disease called diptheria. Adults and teens ages 11 and up should have a shot every ten years. A family doctor will have records of when the last shot was given.