A more thorough explanation:

An annuitant is someone who invests in a pension plan or annuity and is entitled to receive regular payments from it. They are like a creditor, meaning they have a legal right to receive the payments. On the other hand, a beneficiary of an annuity only has an expectation of receiving payments after the annuitant or policy holder passes away.

John invests in an annuity plan and becomes an annuitant. He is entitled to receive monthly payments from the plan for the rest of his life. If John passes away, his spouse may become the annuitant and receive the payments instead.

In contrast, if John had named his son as the beneficiary of the annuity, his son would only receive payments after John and his spouse pass away. Until then, his son would only have an expectation of receiving the payments.

The example illustrates how an annuitant has a legal right to receive payments, while a beneficiary only has an expectation of receiving them.