Motion Graphics is sometimes referred to as VFX (Visual Effects), SFX (Special Effects) or CGI (Computer Generated Imagery) and are graphics that use video and/or animation technology to  simulate the imagined events in a story or create an illusion, usually with motion. It is where video is created and/or manipulated outside the context of a live action shoot. Visual effects often involve the integration of live-action footage and computer generated graphics to create environments which look realistic, or in the case of 'motion backgrounds' to create an interesting background for text or green-screen video like you see in many commercials and news shows on TV.

Basically, adding things like text or fire to video through compositing layers, usually with transparency (alpha channel).  Below are some examples of things we have done.