Codec is a program that encodes and decodes digital data streams or signals. It stands for compression/decompression, but is also referred to as compressor/decompressor or code/decode.
Codec programs work by compressing large files, data streams and signals with the purpose of transmitting, storing or encrypting them, then decoding them for later use. Because codecs shrink data and signals, there is an increase in transmission and download speeds that allow download processing to occur three to five times faster than without the program. Codecs are frequently used for streaming video, music, video editing and videoconferencing. They are required by most media players to play downloaded music, video and movies. While there are numerous codecs available for varying audio and video applications, some of the more common codecs are MP3, WMA, RealAudio and DivX.