While life insurance is designed to help solve the problems created when someone dies prematurely, an annuity is designed to preserve against the possibility of living too long.
Basically, an annuity is a contract between you and an insurance company, which promises to pay you a future income in exchange for the lump-sum payment or premiums that you pay. The payments specified in the annuity contract will be paid to you during your retirement (or, in some situations, to your beneficiaries after your death).
Annuities can be used to help ensure a steady stream of income in retirement, as well as to help ensure that your spouse or designated beneficiary will be taken care of in the event of your death. Many types of annuities exist, and most of them include a death benefit option.