Computer memory usually refers to a form of semiconductor storage known as random-access memory, typically DRAM (Dynamic-RAM) but many times other forms of fast but temporary storage. Without a significant amount of memory, a computer would merely be able to perform fixed operations and immediately output the result. In practice, almost all computers use a variety of memory types, organized in a storage hierarchy around the CPU, as a trade-off between performance and cost.

Another significant type of computer memory module is a flash memory which is a non-volatile computer storage chip that can be electrically erased and reprogrammed. It is primarily used in memory cards, USB flash drives, MP3 players and solid-state drives for general storage and transfer of data between computers and other digital products. Flash memory costs far less than byte-programmable EEPROM and therefore has become the dominant technology wherever a significant amount of non-volatile, solid state storage is needed.