In a cumulative deposit, the interest earned isn't paid out to you periodically — instead, it's automatically reinvested and compounds along with your principal, so you receive one larger lumpsum, combining your original deposit plus all accumulated interest, only at maturity. This option is generally better if you don't need regular income and want to maximise the effect of compounding.
In a non-cumulative deposit, interest is paid out to you at regular intervals — monthly, quarterly, or annually, depending on what you choose — rather than being reinvested, while your original principal is returned separately at maturity. This suits people who want a predictable, regular income stream from their deposit, such as retirees, even though the total amount received over the tenure is somewhat lower than the cumulative option due to the lost compounding effect.