Certificates of deposit (CDs) are time deposit instruments with a bank or brokerage house.
The objective is that you give the institution the money for a period of time. They will tell you up front what the rate of return is, and at the end of that term, you’ll be able to take your money out as well as the interest that you earned during the process.
There are usually penalties associated with taking money out of CDs early, because the instrument is designed for you to have the money available to the institution for a specified period of time.
Sometimes CDs allow you to take advantage of a rollover period if you like the current interest rate and want to continue earning. Otherwise, you can take your money out and either put it back in the bank or use it for something else.