A Civitate is the first rank that a member can achieve. S/he is given this rank only after 100 posts, and has to be nominated by a Civitate who has served out his term. If the member asks for the rank of Civitate, s/he is automatically disqualified from it. The prospective Civitate will be nominated and held in a vote, where the majority wins (however, either an administrator, Consul or other ruler of TWC can veto these votes).
There are many ranks in the hierarchy of members on TWC, Civitate being the foundation. These include Patricians, Senatorii and Magistrates, which are the sub-classes of the Civitates. Civitates can vote in the Curia, against acts which are put forth by the examples of rank I put, and the majority, on this occasion also, swings the vote.
The Curia is a special part of the forum for Civitates and above. This is where legislations are passed and votes are counted. The rules are strict in this sub-section, where off-topic posting and such are harshly punished, compared to other forums.
Personally, the Civitates are the joints of the great TWC forum, who work together with the larger, more useful moderators to help keep the forum alive. The jobs of the Civitates are to keep posts on track, non-flaming and altogether, keep the forum neat and clean. The Civitates are a respected peoples, and should act like such. Therefore, they should act mature, polite and fair in their judgements and comments of other members, or their posts. This, with the help of the mods and the mobs, will help make TWC a better place for us all.