On Rails

Relates to the mechanic of following a predetermined path through an environment. The user has no control over their direction or speed of travel.

Refers to the concept of staying on a predefined path, as in on railroad tracks.

The concept has spawned a popular video game genre, Rail Shooter, in which the player cedes control over movement to concentrate on another task—normally shooting wave after wave of aliens, zombies, or whatever the faceless “baddies” the weak narrative revolves around.

Surrendering control of movement means that the action tends to take place “on rails”. It follows a predetermined path through the game environment where the only parameter the player has any input on is the completion of the set task. Did they kill all the zombies? Yes, move on. No, game over. There is never an opportunity to diverge from the path that’s been hard-coded into the game. Players can’t explore the created environment in any way. They are herded through the game, facing predetermined scenarios, completing set tasks and objectives.
— Klapdor, 2016

Another application of the concept is the idea of Learning on Rails.