Expression pedals. What are they?

[Iggo]

Last year I bought a cheap reverb pedal on Amazon for my “traveling board.” One of those plastic-cased Behringer things. It works. It does reverb.

Anyway, I got a question in my email today from some Amazon questioner. “Can I hook it up to an expression pedal?’

Expression pedals. Don’t have one. Never used one. Always assumed there were wah-wahs, volume pedals, and something else I assumed was more akin to a dimmer switch, kind of an outboard intensity knob in gas-pedal form.

So my first reaction was to say “Sure! Why not?” Then I did a self-check to see if maybe I didn’t know what the fuck I was talking about, and it came up positive.

I’ll let somebody else answer the man’s question. But MY question is:What’s an expression pedal?