It is a low risk and safe investment plan that allows you to earn interest on a lump sum amount that you deposit with a bank for a fixed period of time.
Example:
If you decide to put aside a specific sum of money for your daughter who is likely to get married after 5-7 years, you can save it in a FD (fixed deposit) in the bank. The bank will deposit it for you at the condition that you will not withdraw it before 7 years, giving you interest on your money in return.