The term 'Moco' is short for 'Motion Control' (wikipedia). In general motion control is precise mechanical movement of objects, in our case the object is a camera. The basics of photographic or cinematic motion control are to achieve predictable accurate camera movement and thus smooth changes in point of view. Moves can be made up of a pans (horizontal turn), tilts (vertical turn), dollys (linear travel), rolls (circular camera movement), booms (long arm cantilevers) or any combination of these movements. Photographic and cinegraphic moco can also include control of lens functions such as zoom and aperture. The apparatus that makes all these automated movements and adjustments possible is typically called the 'rig' (which can also refer to non automated or hand driven camera apparatus).