User blog comment:Timeoin/Elder Scrolls Online: Lore Revealed/@comment-23610268-20130925164240/@comment-5247041-20130925165211

200 refers to the number of players that can be on-screen at once. The actual number of players that can be in Cyrodiil at one time is 2,000. It's probably a similar number for the other provinces, although the mega-server technology means it doesn't matter so much how many people are in one region online together.