Players are the people who generate characters and role play those characters in the world presented by the DM or GM.

Without players, the work of a DM will never see the light of day.

A game can be run with a single player, but usually two or three is considered a small game. Many GM’s will not want to run games with more than 8 or 9 players at once. However, there are stories of some DM’s running games with a dozen players at once. Personally, I prefer being a player in games from one to six players. Larger than that seems unwieldy.

In the world of the internet and using Google+ and a Virtual Table Top (VTT), the number of players can be limited by the technology. In the campaign I am playing in we have the DM and seven players. We use Google+ and the Roll20 VTT. We do not use video to speed things up, so it is like a voice conference call. We use Roll20 for dice rolls, intitiative, and showing the position of the players. There is no map. This is very close to how I started playing D&D, so other than the seeing the reaction on other’s faces, is very much like an in-person game.