A video codec is software or hardware that compresses and decompresses digital video. In the context of video compression, codec is a blend of encoder and decoder, while a device that only compresses is typically called an encoder, and one that only decompresses is an decoder.

Video codecs are used in DVD players, Internet video, video on demand, digital cable, television, and a variety of other applications. In particular, they are widely used in applications that record or transmit video, which may not be feasible with the high data volumes and bandwidths of uncompressed video. 

A variety of video compression formats can be implemented on PCs and in consumer electronics equipment. It is therefore possible for multiple codecs to be available in the same product, reducing the need to choose a single primary video compression format to achieve similarities 

The formats that can be seen commonly are:

Avi

Mp4 file format

Mov

Wmv

Mkv

AvcHD

Codecs have their qualities and drawbacks. Comparisons are constantly published. The trade-off between compression power, speed, and fidelity is usually considered the most important figure of technical merit.