closures in functional programming

i ran across this blog posting about the use of a closure to make code maintenance and organization easier. i could use more information, but it seemed useful in terms of getting to know when a function like that would be helpful. i don't really understand very well exactly what a closure is, but i have an idea from the example and from the wikipedia article. it is function that may be used when doing functional programming and may involve anonymous functions accessing variables outside the function's scope.