Video Games Encyclopedia

Shooting gallery games (also known as “target shooting” games) are a sub-genre of shooters where the player aims at moving targets on a stationary screen. They are distinguished from rail shooters, which move the player through levels on a fixed path, and first-person shooters, which allow player-guided navigation through a three-dimensional space.
Shooting gallery games can be light gun games and rail-shooters, although many can also be played using a regular joypad and an on-screen cursor to signify where the bullets are being aimed. When these debuted, they were typically played from a first-person perspective, with enemy fire that occurred anywhere on the screen damaging or killing the player. As they evolved away from the use of light guns, the player came to be represented by an on-screen avatar, usually someone on the bottom of the screen, who could move and avoid enemy attacks while returning fire. These sorts of shooters almost always utilize horizontal scrolling to the right to indicate level progression, with enemies appearing in waves from predestined locations in the background or from the sides. One of the earliest examples is the 1985 arcade game Shootout produced by Data East.
As light gun games and rail shooters became more prevalent and started to make use of scrolling backgrounds, such as Operation Wolf, or fully 3D backgrounds, such as the Time Crisis or House of the Dead series, these sorts of games fell out of popular production, but many like Blood Bros. still have their fanbase today. Other notable games of this category include Cabal and Wild Guns.

Reference: Wikipedia