Most HTPC enthusiasts and other computer users have dealt with codecs. Many have heard the term “codec hell” and in my opinion, one of the ways you keep yourself out of trouble with codecs and make certain you understand chat codec does what for video and music playback is to delve into the different codecs and make sure you understand them.
Adam at the Digital Media Zone has done a great job with a in-depth look at various codecs so I really encourage you to check out the first two parts in his “Understanding Codecs” series: