Welcome to
RPoL (Roleplay Online) is RPG site with proprietary code that includes excellent tools for GMs, including the ability for players to have individual (and multiple) characters in game, each with their own avatar, character sheet, character description, etc.  There is also the possibility to send private messages, create private lines within posts, separate players into private groups, and many more. The community is large, diverse, and active. Adult RPGs are allowed for those 18+, and there are content restrictions on adult content – including keeping such content viewable only to members of the game.   RPoL has other restrictions as well, including not allowing graphic depiction of any non-consensual sexual material or between characters under the age of 18.
Playbyweb is also an RPG site with proprietary code and the ability to have individual characters in game.  It does not offer nearly as many tools as RPoL, and the player base is much smaller.  The activity level and the number of games seems to be declining rather than growing. Adult RPGs are allowed for those 18+, but all adult games automatically have threads hidden in private groups viewable only to those users who are part of the game.
Elliquiy got its start when RPoL’s adult restrictions were put into place, and some long-running and popular  games were asked to comply or move offsite. It has grown tremendously since its start, with an extremely large and active membership.  While it is geared toward adult roleplay, it also has a section for non-adult games and stories.
Eyes are the     Window to the Soul  Our souls sit close and silently within,  And their own webs from their own entrails spin;  And when eyes meet far off, our sense is such  That, spider-like, we feel the tenderest touch.  -- John Dryden