The difference between volatile and non-volatile memory hinges on data retention when power is lost. Volatile memory, such as DRAM and SRAM, requires continuous power to maintain data—losing it when power is cut, which is why system RAM clears on shutdown. Non-volatile memory, like NAND and NOR flash, preserves data without power, making it ideal for storage in SSDs, USB drives, and firmware.

Volatility describes only power-dependent data survival, not speed, capacity, or function. DRAM, the main working memory in computers, uses capacitor-transistor cells needing constant refresh; SRAM, faster and refresh-free while powered, serves CPU caches. NAND flash dominates consumer storage via SSDs, while NOR flash stores boot code in embedded systems.

Both volatile and non-volatile categories include multiple technologies serving distinct roles, with modern devices combining them for performance and persistence.