Side-scroller

A side-scrolling game, side-scroller or 2D is a video game in which the gameplay action is viewed from a side-view camera angle, and the onscreen characters generally move from the left side of the screen to the right (or less commonly, right to left) to meet an objective. These games make use of scrolling computer display technology. The move from single-screen or flip-screen graphics to scrolling graphics, during the golden age of video arcade games and during third-generation consoles, would prove to be a pivotal leap in game design, comparable to the move to 3D graphics during the fifth generation. Although side-scrolling games have been supplanted by 3D games, they continue to be produced, particularly for handheld devices or for digital-only releases.

A common use of the side-scrolling format is in the platform game genre. Platform games are action games that feature jumping, climbing, and running through many diverse levels. Games such as Super Mario Bros. are among the most famous side-scrollers of this type.

The side-scrolling format is also popular among beat 'em ups, such as the popular Battletoads series. Side-scrolling is sometimes used in certain role-playing video games such as the 2D Castlevania: Symphony of the Night or the Korean MMORPG MapleStory. Often in beat 'em ups the screen will scroll to a certain point then stop and require the enemies on screen to be defeated before it moves on.

...
Wikipedia