ROM (Read-Only Memory) is a computer memory on which data can be recorded only once. Once data has been written on ROM, it cannot be deleted but can be read as many times as required.
ROM mainly contains firmware software which is generally prerecorded by the manufacturing company.
Unlike RAM, ROM retains its contents even if the power is turned off and thus it is a non-volatile memory.
Note: ROM is often used in other devices such as calculators.