Motion graphics are digital footage and/or animation technology to create the illusion of motion or rotation, and are usually combined with audio for use in multimedia projects, film titles and advertising. (From Wikipedia)
Motion graphics is simply the manipulations of objects in 2D or 3D space set in motion to get across a specific idea or ideas. It can be the opening titles to a film, an advertisement or an educational piece. It can involve text and objects that all serve to tell a story in a non-static way.
Examples of Motion Graphics from Tomorrows World Video