Bandwidth can be imagined as being analogous to the internal diameter of a water pipe, the larger the diameter the more water will flow- thus the larger the bandwidth the more data can flow and in this case, the better the video.

Compression is a mathematical technique used in the software and hardware which uses "tricks" to squeeze better quality video for a particular available bandwidth.

Technologies listed here are as of 1999 and by observation change on a 3-6 month cycle with new technologies appearing and old ones fading out. As time passes some of the older technologies repackaged an reappearing at more advantageous times.