An annuity is a financial plan that pays out a predetermined amount to you at pre-decided intervals for a specific duration or for the rest of your life. You can get a lump sum annuity or monthly or even annual annuity. An annuity is usually used in the context of insurance, where you invest a certain amount through premiums and earn a payout during retirement. You can choose from various annuity plans such as immediate, fixed and variable.