A closure can be reconverted into a block, so a closure can be used anywhere a block can be used. Closures are used to store the status of a block into an instance variable, once you convert a block into a closure, it is becomes an object that can by referenced by a variable. Just as they are used in other languages, closures can be passed around the object to customize behavior of methods. To pass some code to customize a method, just pass a block. But if you want to pass the same code to more than two methods — convert the block into a closure, and pass that closure object to multiple methods.