Dead Space: Extraction is a prequel to the video game Dead Space. Dead Space: Extraction takes place before the events of Dead Space. It revolves around a group of space colonists from the Aegis VII colony fighting against the infection of Necromorphs created when the Red Marker is removed. Necromorphs are the re-animated, mutated corpses of dead humans and serve as the major antagonists of the game.
Extraction is a first-person rail shooter introducing new enemies, characters, weapons and environments to the Dead Space series. Players also have some degree of control over the camera.
Source: Wikipedia, "Dead Space: Extraction", available under the CC-BY-SA License.