What's the difference between a flash drive and a USB flash drive

U disk and flash disk belong to memory, U disk is USB port flash disk, flash card is just different from the interface of U disk. Flash memory, this is a separate concept, simply put, U disk and flash memory card used in the storage part, called flash memory. The following is the definition of FlashMemory: Flash memory is a kind of long-lived non-volatile (in the case of power failure can still retain the stored data information) memory, data deletion is not in a single byte unit but in a fixed block size, block size is generally 256KB to 20MB. Flash memory is a variant of electronically erasable read-only memory (EEPROM), which differs from flash memory in that it can be erased and rewritten at the byte level rather than the entire chip, allowing flash memory to be updated faster than EEPROM. Because it can still save data when it is powered off, flash memory is often used to save configuration information, such as in the computer's BIOS (basic input and output program), PDA (personal digital assistant), digital camera to save data. Flash memory, on the other hand, does not rewrite data in bytes like RAM (random access memory), so it cannot replace RAM.