The K-Lite Codec Pack is a collection of DirectShow filters, VFW/ACM codecs, and tools. Codecs and DirectShow filters are needed for encoding and decoding audio and video formats. The K-Lite Codec Pack is designed as a user-friendly solution for playing all your audio and movie files. With the K-Lite Codec Pack you should be able to play all the popular audio and video formats and even several less common formats.
K-Lite Codec Pack standard variant contains everything you need to play all the common video file formats. It contains Media Player Classic, which is an excellent player for video files. It also has (better) support for playback of DVDs. This pack is recommended for the average user.
There are a lot of good codec packs out there, but a lot contain illegal codecs. K-Lite Codec Pack (Standard) contains nothing but legal and clean codecs. Here you can find a list of all components that are included in the pack.