Can u tell me the difference between mp3 and mp4 file format. Why mp4 format file didn't play in windows media player.

MP3 is a format used to store audio in a compressed manner. MP4 is a container which can be used to store audio and video as well as other information. MP3 is compressed and is used within the limited confines of audio reproduction.

Since MP4 is actually a container, the types of compression used inside the container can be different. Of course, it can also contain streaming video in addition to audio. You could also store other information in the MP4 like Closed Captioning text. An interesting fact, inside the MP4 container, you could have a video file and an audio file compressed in the MP3 file format.