Compression, or "data compression," is used to reduce the size of one or more files. When a file is compressed, it takes up less disk space than an uncompressed version and can be transferred to other systems more quickly. Therefore, compression is often used to save disk space and reduce the time needed to transfer files over the Internet.
There are two primary types of data compression:
File compression can be used to compress all types of data into a compressed archive. These archives must first be decompressed with a decompression utility in order to open the original file(s). Media compression is used to save compressed image, audio, and video files. Examples of compressed media formats include JPEG images, MP3 audio, and MPEG video files. Most image viewers and media playback programs can open standard compressed file types directly.
File compression is always performed using a lossless compression algorithm, meaning no information is lost during the compression process. Therefore, a compressed archive can be fully restored to the original version when it is decompressed. While some media is compressed using lossless compression, most image, audio, and video files are compressed using lossy compression. This means some of the media's original quality is lost when the file is compressed. However, most modern compression algorithms can compress media with little to no loss in quality.