A V.F.D. Chaperone is a V.F.D. member who takes a V.F.D. Apprentice in order to teach them everything they need to know about working within V.F.D. There are, at the time of Lemony Snicket's apprenticeship, 52 chaperones of V.F.D. who are ranked on a list for the apprentice to choose from.
The chaperones of V.F.D. want what is best for the apprentices. In fact, in a desperate attempt to give Lemony the best education possible, Lemony's supposed mother and father try to rend him unconscious by drugging his tea. In doing this, they try to deter him from taking an apprenticeship with S. Theodora Markson who was listed as the worst chaperone, ranked 52 of out 52.