The capability to track hands and recognize hand gestures
The capability to recognize one or more users and track their movements
The capability to recognize different parts of the user's body and extract his/her skeleton map and joint positions
Please note that you don't need NiTE if you want to simply work with depth/IR or Image stream. But if you want to go one step forward and work with the middleware layer, you need to install NiTE and use it.
Without NiTE, we can only use low-level data such as the output of different physical sensors of one or more devices.