MPEG format is a standard for lossy compression of video and audio and it is the most compatible multimedia format.
This format is largely used for sharing movie trailers and music videos over the Internet, but users typically convert them to more popular formats once they download them.
Additionally, users also need to convert MPEG video to other format in order to play them on certain devices (such as mobile phones or iPods).
Either way, MPEG files can also be played the software applications that support converting them.