Telesync is one of many terms used by movie bootleggers to describe the source material used to make bootlegged copies, normally distributed in Video CD, SVCD, DVD or DivX/Xvid format. It is commonly abbreviated TS.
A TS is a video copy of the movie which was shot in a movie theater, often with a professional camera on a tripod in the projection booth, with a direct connection to the sound source (often an FM-band microbroadcast provided for the hearing-impaired, or from a drive-in theater). However, the true definition of Telesync would include the film being syncronised to the camera's own frame capture rate (FPS) and shutter timing as done by television companies when preparing cellulose film for broadcast. Bootleg TS rarely, if ever, utilise this form of syncronisation which can lead to additional temporal aliasing.
A CAM is a video copy of a movie usually shot with a hand-held camera from a seat in the auditorium and uses the camera's own built-in microphone to pick up the sound. Usually, the quality is quite poor.
A TS can be considered a higher quality type of CAM, that has the potential of better-quality audio and video.
As technology gets better, the quality of the telesyncs also gets better, though it should be noted that even the best telesyncs are lossy and will be inferior in quality to direct rips from BD, DVD or digital transfers from the film itself (telecine). Although very few at the moment, some release groups use high-definition video cameras to get the clearest picture possible