Podcasting Tools :: Free-Codecs.com
" Short for compressor/decompressor, a codec is any technology for compressing and decompressing data. Codecs can be implemented in software, hardware, or a combination of both. Some popular codecs for computer video include MPEG, Indeo and Cinepak" from
http://www.xilinx.com/publications/glossary.htm
So if you are having trouble translating a version of video that you created, into a smaller file that can be distributed on the net, the Free-Codecs.com site may have your answer.