CODEC stands for Compressor-Decompressor. It is the primary method used in the authoring and playback of DVD/Blu-ray video. A codec is used to reduce file size (compress) so it will fit on a DVD or Blu-ray disc. The video is first compressed to reduce the file size to fit on a disc and then decompressed for playback to try and recreate the original pre-compressed video image. A CODEC is the software device used to accomplish this. There are many different CODECS that can yield a wide variety of results.