Compressing digital data means removing redundancies so that it takes up less space. There are two main forms of compression, lossy and lossless. Lossless compression only takes away a certain amount of data so that it can be returned to its original complete state. Lossy compression however, will sacrifice more data to produce better compression. MPEG-4 is a lossy compression that can keep high quality but can reduce the amount of space a video file needs tremendously.