[mtomczak]

They are functions you can make up on the spot. That's usually the extent of my explanation.

Surprisingly, most of the people I talk to assume that the "fancy" parts of closures (such as variable value capture and upvalues) are the way such a construct should work and require no further explanation to use them. People who are surprised by capture (and assume, for instance, that the variable will take on the most recent value assigned to it by outside code instead of "remembering the value when the closure was made") get a more lengthy computer science-esque explanation. But I generally find that explanation to be unhelpful if a person can't see why closures are useful; "An anonymous function with some teeth" is often how people I talk to come to closures first, so it's how I let them think about it until the model is no longer helpful.

[DanielStraight]

Right. That's exactly how it was with me when I first encountered closures. Explaining something that would be guessed anyway just makes it seem more complicated than it is.