How to understand flash memory

Flash memory is a type of nonvolatile memory that erases data in units called blocks. A block stored on a flash memory chip must be erased before data can be written, or programmed, to the microchip.

Flash memory retains data for an extended period of time whether a flash-equipped device is powered on or off.

Flash works using an entirely different kind of transistor that stays switched on (or switched off) even when the power is turned off.