In MotionBuilder, a timeline represents the length of your animation using time codes or frame numbers and has a Timeline indicator that marks the current time. Though the Transport Controls window contains the main timeline options, the Dopesheet, FCurves, and Story windows also display this timeline.

MotionBuilder has two timelines; the Action timeline and the Edit timeline. The Action timeline is the main MotionBuilder timeline, where you create and edit animation. All windows with a timeline use the Action timeline. The Edit timeline is used in the Story window to edit the scene with camera shots and time discontinuity.