A USB Flash Drive is essentially NAND-type flash memory integrated with a USB interface used as a small, lightweight, removable data storage device. This hot-swappable, non-volatile, solid-state device is universally compatible with post-Windows 98 platforms, Macintosh platforms, and most Unix-like platforms.
USB Flash Drive are also known as "pen drives", "thumb drives", "flash drives", "USB keys", "USB memory keys", "USB sticks", "jump drives", "keydrives","vault drives" and many more names. They are also sometimes miscalled memory sticks (a Sony trademark describing a different type of portable memory).
A flash drive consists of a small printed circuit board encased with a robust plastic casing, making the drive sturdy enough to be carried around in a pocket, as a keyfob, or on a lanyard. Only the USB connector protrudes from this plastic protection, and is often covered by a removable plastic cap. Most flash drives feature the larger type-A USB connection, although some feature the smaller "miniUSB" connection.
Flash drives are active only when powered by a USB computer connection, and require no other external power source or battery power source; key drives are run off the limited supply afforded by the USB connection (5V). To access the data stored in a flash drive, the flash drive must be connected to a computer, either by direct connection to the computer's USB port or via a USB hub.