Interest is the return on your investment. There are various types of accounts facility offered by the Bank to attract deposit. The Investment are in the nature of Short Term and Long term. In Saving Bank (SB) A/c the liquidity is very high you can withdraw when ever you want. Here the rate of Interest which you might receive is generally low.
In Fixed Deposit (FD) the term of deposit is fixed and you can not withdraw money before the end of period. Here the rate of Interest is high. At the time of Maturity you receive Principal and Interest
In recurring Deposit (RD) you have to deposit a fixed amount on monthly/daily basis up to a certain period of time and after that you will receive Principal+ Interest) Here also there is a lock in period.
As regards the Interest on Loan is concerned it is the Interest which we generally pay on taking a loan from a Bank