File and suspend is a strategy available only to those who elect to wait until at least their normal retirement age to begin receiving Social Security benefits. It is a tool that allows the coordination of benefits between spouses and is a bit like an insurance policy for anyone deferring benefits. It works like this.
Once you reach your normal retirement age you apply for Social Security benefits, but have your payment suspended before any check are issued. This accomplishes two things. One, if you have a spouse who is eligible for spousal benefits it is a signal to the Social Security Administration that they can now claim those benefits. Two, it provides some protection in case you learn you have a medical condition that will limit your lifespan. If, for example, you are diagnosed with cancer when you are age 69 and not expected to live much longer, you can go back to the Social Security Administration and tell them you want to receive benefits retroactively to the day you had your benefits suspended. You will receive a lump sum check for any benefits accrued up to that point.
If you do not retroactively claim your benefits you will continue to earn delayed retirement credits and boost your monthly check by 8% a year until you reach age 70.