Programmable Read-Only Memory (PROM) is a type of non-volatile memory that retains data even when the power is turned off. Unlike standard Read-Only Memory (ROM), PROM can be programmed once after its manufacturing. This means that users can write data to it, but once programmed, the information cannot be changed or erased. PROM is commonly used in applications where permanent data storage is required, such as in firmware for computers and embedded systems. Its ability to hold data securely makes it a reliable choice for storing essential instructions that devices need to operate correctly.