1) Primary storage, also known as main storage or memory, is the main area in a computer in which data is stored for quick access by the computer's processor. On today's smaller computers, especially personal computers and workstations, the term random access memory (RAM) - or just memory - is used instead of primary or main storage, and the hard disk, diskette, CD, and DVD collectively describe secondary storage or auxiliary storage.
The terms main storage and auxiliary storage originated in the days of the mainframe computer to distinguish the more immediately accessible data storage from storage that required input/output operations. An earlier term for main storage was core in the days when the main data storage contained ferrite cores.
2) Primary storage is sometimes used to mean storage for data that is in active use in contrast to storage that is used for backup purposes. In this usage, primary storage is mainly the secondary storage referred to in meaning 1. (It should be noted that, although these two meanings conflict, the appropriate meaning is usually apparent from the context.)