Matchmoving is the computation of the global 3D geometry of a scene including camera path, internal parameters, and moving object. By exporting the real 3D camera path and parameters to animation software, the position and motion of virtual cameras can be accurately established. With the motion of the virtual cameras, new, matched image sequences can be created whose virtual objects are seamlessly composited into live action footage.
Here is a very basic example. The Handycam was captured with 123D, then placed into real life footage at the end of this video:
Autodesk MatchMover 2014: About Autodesk MatchMover