When I was younger I used to collect Video Game magazines (mostly Playstation) which would review games like they do. Some of the magazines have described some games as being "On Rails" - I have no idea what that is (I assume it's something bad?) does anyone know?

By the way, I haven't seen the term used during actual reviews, but the "buyers guide" at the end of the mags, where they have the game's name, a score, and a comment.