what is mp4?
An ISO/IEC standard 14496 developed by the Moving Picture Experts Group (MPEG).MP4 is a new container format, a container format allows you to combine different multimedia streams into one single file. MP4 is streamable and supports all kinds of multimedia content.

What is MPEG?
MPEG stands for Moving Pictures Expert Group.
MPEG-1 is the video format that has had some extremely popular spin-offs and side products, most notably MP3 and Video CD.
MPEG-2 is not a successor for MPEG-1, but an addition instead. MPEG-2 is used in digital TVs, DVD-Videos and in SVCDs. An ISO/IEC standard 14496 developed by the Moving Picture Experts Group (MPEG).MP4 is a new container format, a container format allows you to combine different multimedia streams into one single file. MP4 is streamable and supports all kinds of multimedia content.

what is AVI?
AVI is an acronym for Audio Video Interleave. This is basically a multimedia container format and was first released by software giant Microsoft in November 1992.