Flash unit
From The Glossary of Digital Photography
A separate lighting device that produces a brief flash of very bright light to light a scene. Flash units are usually electronically powered. A flash unit can attach directly to a camera with a shoe mount, or it can be a studio unit that is mounted on a stand. A flash unit can be powered by batteries, either disposable or rechargeable, or by standard electrical power. The price can vary from a few dollars to many hundreds or even thousands of dollars. The duration of the flash is typically around1/1,000th of a second. See also flash duration
