<p>I've been reading a lot about closures and I think I understand them, but without clouding the picture for myself and others, I am hoping someone can explain closures as succinctly and clearly as possible.  I'm looking for a simple explanation that might help me understand where and why I would want to use them.</p>

It's simple: A function that references variables from a containing scope, potentially after flow-of-control has left that scope. That last bit is very useful:
```
```
>>> def makeConstantAdder(x):
...     constant = x
...     def adder(y):
...         return y + constant
...     return adder
... 
>>> f = makeConstantAdder(12)
>>> f(3)
15
>>> g = makeConstantAdder(4)
>>> g(3)
7
```
```
Note that 12 and 4 have "disappeared" inside f and g, respectively, this feature is what make f and g proper closures.