The Defination of Codec Pack
To learn about "what is a codec pack", you must firstly know what a codec is! Put it simply, a codec is a program created to encode or decode digital data into something that your computer can understand and play. Figuratively, a codec is like a key and the video audio format is the lock, so to open a video/audio, you need the right key.
A codec pack, just as its name implies, is a collection of different codecs that enable the operating system (Windows/Mac/Linux) and its software to play various video and audio formats generally not supported by the system or the software itself. With codec packs, you can strengthen your computer with a number of different codecs at one installation. Basically, a codec pack contains the most wide-used audio video codecs such as AVI, DivX, MPEG-4 (.mp4/.m4v/.m4a), MPEG-2, FLV, MKV, MP3, OGG, FLAC, etc. Some more advanced codec packs also include lots of obscure codecs like AC3, ALAC, AMV, MPC, XM, OFR, OFS, and so on.