Cam movies are very rough bootleg copies made by moviegoers who video tape a film while sitting in a theater.  This process is illegal and can get a person fined, thrown in jail and sued by movie studios if caught.  People make cam movies so that others do not have to pay movie theater fees to see a new film.  This usually occurs because some people cannot get to a theater, people do not want to pay such a high fee to see a new movie, some folks may not be sure about seeing a new film depending on its reviews or another reason.  Even if you want to see a new movie and cannot afford it, it is illegal to obtain or make a cam movie as it infringes on a movie studio's copyright on said film.

A cam movie is made when a moviegoer sneaks a video camera into a movie theater.  They try to obstruct it from view for the duration of a film while capturing what happens on screen as well as the audio involved.  Due to the random nature of movie going, everything from coughing, popcorn eating, drinking and more can interfere with the picture and audio quality of a cam movie.  Thus, those who are skilled in audio and video editing may work with the cam movie rough draft before releasing it to those looking to download a bootleg copy of a new release before the DVD comes out.

Cam movies are generally the worst quality film bootleg out there.  While some folks are desperate to see a new movie, they may not like the quality of illegally obtaining one.  Video and sound are often distorted, cut off or otherwise interfered with because of the movie theater atmosphere.  For example, if a video camera is being hidden by a jacket, any movement of that jacket or the person holding the camera may shake the picture, cut off part of the screen or otherwise obstruct the film.  In addition, if the person next to you is talking, that will be picked up on the cam movie and you will hear that conversation.  In general, cam movies are not worth the time or effort in downloading illegally because they are so low in quality.