A hot shoe, also known as an accessory shoe, allows an external flash or other device to be connected to a camera. A hot shoe is a slotted bracket that is generally located on the top of a camera.
When an external flash is inserted into the the hot shoe, it’s electrical contacts touch the contacts on the foot of the flash. If there is only one contact (metal circle) then your camera can use a manual external flash, if there are more then your camera is compatible with a dedicated (fully automatic) flash probably from your cameras manufacturer (check your manual).
When the shutter-release button is pressed, the flash goes off in sync with the shutter.
When a camera doesn’t have a hot shoe
Though almost all digital cameras have a built-in flash, not all have a hot shoe. It is primarily found on advanced compact digital cameras and digital Single Lens Reflex cameras.
If your digital camera doesn’t have a hot shoe but you want some of the benefits of using an external flash, get a slave flash. A slave flash in an external unit that is triggered when the built-in camera flash goes off.
Slave flashes often come with a bracket. The flash is mounted on the bracket, which attaches to a tripod mount on the bottom of a camera.
The down side to using a slave flash is that it may trigger your flash if someone uses a flash near you.