The mechanics that allow your garage door to lift and lower involve the cables on either side of the door frame. The door is lifted through a transmission of energy from the springs attached to the door, the garage door opener, and the tracks. These forces all work together, but if one fails, such as a cable snaps or falls out of a drum, the garage will not function at all and will either fall or be unable to lift.
Garage door cable repair can be difficult and dangerous, but with the right help, it can be done properly.