A definition of Grip
Sometimes called a battery grip, this is an accessory which screws into a DSLR or similar camera, with two main purposes. First, the it can aid portrait shooting, as it allows the camera to be held in a portrait orientation with a feel similar to it being held conventionally. For this reason, a shutter release button, command dial and certain other controls will be typically incorporated into its design. Second, by including one or more batteries in its body, a grip can extend the effective battery life of a camera.