An annuity is a contract between you and an insurance company in which the company promises to make periodic payments to you, starting immediately or at some future time. You buy an annuity either with a single payment or a series of payments called premiums.

Some annuity contracts provide a way to save for retirement. Others can turn your savings into a stream of retirement income. Still others do both. If you use an annuity as a savings vehicle and the insurance company delays your pay-out to the future, you have a deferred annuity. If you use the annuity to create a source of retirement income and your payments start right away, you have an immediate annuity. 

The two most common types of annuities are fixed and variable. There is also a hybrid called an indexed annuity, also referred to as an equity-indexed annuity or a fixed-index annuity. Variable annuities are securities and under FINRA's jurisdiction.

Annuities are often products investors consider when they plan for retirement—so it pays to understand them. They also are often marketed as tax-deferred savings products. Annuities come with a variety of fees and expenses, such as surrender charges, mortality and expense risk charges and administrative fees. Annuities also can have high commissions, reaching seven percent or more.

Types of Annuities