AVI: Audio Video Interleave. A format developed by Microsoft and described as a container encapsulating video and audio files that are themselves written in other formats. An AVI file (extension .avi) can also hold MPeg or DivX video files, or MP3 encoded music.
To read a file there has to be a "codec" in the player corresponding to the encapsulated file formats. A codec (coder-decoder) is a program that can decrypt an audio or video file.
So a computer will not necessarily be able to play all AVI files. For example, if it does not have the DivX codec it will not be able to play AVI files that include DivX videos.
Many camcorders (here, the Continental Edison D36 FT) produce files in AVI format. © Continental Edison