The nuts and bolts of an annuity boils down to some very basic contracting. You, as the investor, pay a lump sum amount to the annuity issuer, typically an insurance company. At a pre-defined period, typically your retirement, the annuity would mature and start paying you a fixed amount every month. The advantage of an annuity is that you will not have to pay taxes until the annuity payments actually start accruing to you. Although considered low risk, annuity provides charge high fees and their success is largely dependent on the reputation and stability of the insurance company underwriting the annuity.