A CD-ROM (Compact Disc Read-Only Memory) is a type of optical disc that stores data in a digital format. It was widely used in the 1990s and early 2000s for distributing software, games, and multimedia content. Unlike regular CDs, which can be written to and erased, CD-ROMs are designed to be read-only, meaning the data cannot be modified once it is written. CD-ROMs typically hold up to 700 megabytes of data, making them suitable for various applications, including educational materials and operating systems. They require a CD-ROM drive to read the data, which uses a laser to access the information stored on the disc's surface.