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).

OpenMoCo

Motion control is quickly becoming the must have tool for professionals and enthusiasts capturing video, time-lapse, panoramic photography and image based lighting. Typically accurate motion control comes with a hefty price tag and little flexibility.  The OpenMoCo.org mission is to provide a community for open-source software and hardware that enables photographers and videographers on a budget access to motion control tools.  Here you'll find articles, hardware designs, software, and experiments in motion control.

The OpenMoCo Reference Design

The OpenMoCo Reference Design was originally created by Chris Church (shutterdrone) for experimenting with steppers and motion controls for timelapse use.  It has since grown to support different forms of motion control, such as gigapixel panoramas, stereoscopic shooting, and more, and has been adapted by many individuals to their specific needs.