MPG is a video format that combines MPEG-1 or MPEG-2 video formats as well as audio formats. Without losing the quality it compresses the VHS-quality raw digital videos. MPG, standardized by Moving Picture Experts Group, supports Mac, Windows or other OS.
MP3 is an audio format that can compress and encode an audio file. It uses the lossy compression algorithm to contain audio data. The lossy compression helps to reduce the data significantly without losing audio quality. MP3s are created using different bit rates maintaining the original quality.