O que é um fechamento: explicação informal

-Closures are a bit like classes.
-They have a function inside of them. 
-Closures return a function. 
-You can create an "instance" of a closure with new Closure(). 
-Everytime you execute the "instance" you are executing the returned function.
-Counter is the most famous example: everytime you execute a counter() instance, you execute the "increaseCounter" function being returned
Javasper