There are two basic types of annuities: deferred and immediate.
With a deferred annuity, your money is invested for a period of time until you are ready to begin taking withdrawals, typically in retirement.
If you opt for an immediate annuity you begin to receive payments soon after you make your initial investment. For example, you might consider purchasing an immediate annuity as you approach retirement age.
The deferred annuity accumulates money while the immediate annuity pays out. Deferred annuities can also be converted into immediate annuities when the owner wants to start collecting payments.
Within these two categories, annuities can also be either fixed or variable depending on whether the payout is a fixed sum, tied to the performance of the overall market or group of investments, or a combination of the two.