Adobe After Effects is a media production program that is used to composite and creates motion graphics and visual effects. Motion graphics consist of any moving graphical image ranging from video billboards, graphics used in television commercials, and movie title sequences.  Visual effects consist anything that is composited.  Compositing is the combining of multiple elements to create a new image.  This includes effects in movies, color correction, green screen removal.  Whereas video editing programs are based on horizontal timelines (focusing on longer time sequences), After Effects is a vertical editor (often with shorter lengths of footage but multiple layers like in Photoshop).