An annuity is a contract between you and an insurance company that requires the insurer to make payments to you, either immediately or in the future. 
A mortgage is a loan used to purchase or maintain a home, plot of land, or other real estate. The borrower agrees to pay the lender over time, typically in a series of regular payments divided into principal and interest. The property then serves as collateral to secure the loan.
Amortization calculator

A = periodic payment amount
P = amount of principal, net of initial payments
i = periodic interest rate
n = total number of payments