A hot shoe flash is a removable flash that can be mounted on a camera's hot shoe.
Hot shoe flashes, also called speedlights, are battery powered, portable, short-duration photographic lights. With the exception of Sony, they use a standardized mount, with a single center pin for firing. Many modern models also have additional pins for more complicated — and system-specific and usually proprietary — communication.
Many "hot shoe" flashes may also be mounted in cold shoe and triggered remotely, whether by cable, optical signals, or radio.