NAND flash is a type of non-volatile storage technology that retains data even when the power is turned off. It is commonly used in devices like USB drives, memory cards, and solid-state drives (SSDs) due to its ability to store large amounts of data in a compact form. This technology works by using memory cells made of floating-gate transistors to store bits of information. NAND flash is faster and more durable than traditional hard drives, making it a popular choice for modern computing and mobile devices.