Both are ways of keeping money in a bank so that it grows. Here they are in the simplest words.
Fixed Deposit (FD) — you give the bank one lump of money once, and promise not to take it out for a fixed time — say one year, or five years. The bank pays you more interest than it pays on a savings account, because it knows you will not take the money back tomorrow.
Example: You put ₹1,000 into an FD for one year. At the end of the year the bank gives you back your ₹1,000 plus the interest it promised.
Recurring Deposit (RD) — you promise to put in a small, equal amount every month for a fixed number of months. It is a way of saving little by little.
Example: You put ₹100 into an RD every month for 12 months. You have put in ₹1,200 in all, and at the end the bank returns that ₹1,200 plus interest.
How to share it with your class: Draw this table on a chart. Bring a real passbook or an FD slip from home if you can. Then explain the two words with your own example — “If I save ₹100 from my pocket money every month, that is a recurring deposit.”
The idea behind all three: A bank lends your money to somebody else who needs it. It earns something for doing that, and it shares a part of that with you. The longer you promise to leave your money there, the more it can do with it — and the more interest it pays you. That is the whole rule.