Today I notices that we must have some moderators on this site, as on of the questions was closed.
So by now we know some or most of the current moderators.
How did they become moderators?
You don't need moderators to close questons -- once your reputation is high enough (which is 1 right now, 250 when we're out of beta), you'll get an option to vote to close -- any 5 non-moderator users can then close a question.
For example, no moderators were involved for:
If there were moderators involved in a close, there would be a diamond next to the last person in the list (and typically less than 5 people in the list, as if a moderator votes, it's closed immediately)