The Player Moderator Centre is a special area of the RuneScape website, restricted to Player Moderators (and Jagex Staff) only. Players trying to access the Player Moderator Centre on an account without Player Moderator status will receive a page thanking them for their interest in Player Moderators and advising them to visit the Knowledge Base.
The Player Moderator Centre contains tools and information for Player Moderators. These include a set of guidelines, a Moderator Code of Conduct, forums exclusively for Player Moderators, among others. Jagex has not publicly released any information beyond what is mentioned here.
When a player first becomes a moderator, they must read and agree to a strict and expanded Code of Conduct. Within the Player Moderator Centre, Player Moderators have the ability to register their account with Jagex, directly contact Jagex, and get access to the moderator-only forums.