MP4, short for MPEG-4 Part 14, is a very popular multimedia file format using MPEG-4 to store videos, audio, subtitles and still images.
WMV (Windows Media Video) is a popular stream media format developed by Microsoft. Initially, WMV was designed to be used by Internet streaming applications to compete with RealVideo.
AVI, known as Audio Video Interleaved, is a container format specially developed to store audio and image into a single file for simultaneous playback.
FLV also known as Flash Video is a popular container file format commonly used for streaming online video, which can be embedded to any online sharing website such as Youtube, Yahoo Video, Google Video etc.