What is purpose of delegates?

Question

The delegation is a commonly used pattern in object-oriented programming. It is a situation where an object, instead of performing a tasks itself, delegates that task to
another, helper object. The helper object is called the delegate.
Or
A delegate is a pointer to an object with a set of methods the delegate-holder knows how to call. In other words, it's a mechanism to enable specific callbacks from a later-created object.