@Incandescent if you happened to be on TB in the past, the admins used to be "nominated" by the BMBs. But, as @caitlyn5454 said above, it's actual people that work for TB now that are admins/moderators.
***TW in Siggy*** Me: 34 / DH: 33 Married: Nov 2011 TTC #1: Jan 2013, BFP Sept 2013, DD: June 2014 TTC #2: Aug 2016, BFP Nov 2016, DS: August 2017