Just a quick question which I can't seem to find an answer to. What is an auxiliary snare? I keep hearing about drummers talking about their auxiliary snares, but I have no idea what they're talking about, or what an auxiliary snare is used for.
It's just an additional snare (auxiliary means backup) besides the main one, usually positioned to the left of the hi-hat. Generally they're either larger or smaller (wider and taller/shorter) than the main snare, just so one has different sounds available.
^this is correct. A lot of times it will be a piccolo snare.