Factory Method Pattern的实际用途是什么？

I'm pretty new to Design Patterns.I just came across Factory Design Pattern. I understood that it delegates the instantiation to subclasses. But I didn't get the actual application of the pattern. In which scenarios can this pattern be used to good effect. I've heard of pattern abuse and would not like to indulge in that. Can anyone mention a real world example where it is commonly used. I'm pretty new to Design Patterns.I just came a