A movie is a file containing a sequence of frames from Whorld's animation. After a movie has been recorded, it can be played in Whorld, but to use it in another application, it must be exported first.
Movie frames are stored in a non-lossy format, so that the animation can be restored later exactly as it was, with no loss of information. Movies are implemented using snapshots, so they're vector-based, rather than pixel-based.
Movie files can be quite large. Typical data rates range from 0.5 to 3.0 MB per second, which means a 1-hour recording can require anywhere from 1.5 to 10 GB. In practice, movies are often at the low end of this range. A movie stores the ring data for each frame, which means a movie's size is proportional to the average number of rings. Various factors can affect the number of rings; see performance.