Many of us do not think twice about the usage of our digital camera's flash assuming that the camera will use the flash automatically as needed. Flash however can and should be manually set in many scenarios resulting in high quality digital photos.
The most common usage of flash photography is when there is not enough ambient light for example when taking an indoor digital photo in a dark room. There are many other ways in which you can use your digital camera's flash to get high quality digital photos. One such usage is fill-in flash.
Before setting your flash to manual mode and making more efficient usage of it you should know a bit more of the technology and history behind flash photography. Flash photography has been around for more than a century. During the early days of photography flash was implemented as a powder that was literally lit by either fire or electrical current. At that time flash photography was a risky business. Digital cameras today use a safe implementation by utilizing electronic flash tubes that are automatically synchronized with the camera's shutter.
You have two options for using flash with your digital camera. The first option is using the digital camera internal flash. Practically all digital cameras have build-in flash units. Most cameras also allow the usage of an external flash unit. Such flash units can be either mechanically attached to the digital camera or they can be connected to the camera via a cable and mechanically positioned on a tripod or any other mechanism. They are synchronized and controlled by the digital camera. External flash units vary in price and features. They can have different maximum light energy that they can emit and different mechanical capabilities (tilting, skewing).