The item you purchased is a Pro Battery Grip for Canon EOS 5D Mark II. It can hold 6 AA batteries or two LP-E6 li-ion batteries, doubling the battery capacity of your camera. Vertical shutter release button on the Battery Grip makes shooting with the camera in a vertical position much easier, adding stability to the camera.

In this professional edition, it comes with several functional buttons as the flash above showing. It will be much convenient while using. It provides additional shutter release, main dial, AE lock/FE lock and AF point selection controls for easier vertical shooting. Having the same function as Canon BG-E6!