No matter how you slice up conferencing solutions, the categories you use to group them are mutable and subject to instant revision. Combinations of various elements make some applications basically impossible to categorize. Depending on how you look at it mail lists are even a form of conferencing and so is email. Real-time versus asynchronous is even becoming blurred as text, audio and video merge in varying combinations.

That said and out of the way, lets look at some of the ways conferencing solutions are categorized.