An abstract class is a class that is only partially implemented by the programmer. It may contain one or more abstract methods. An abstract method is simply a function definition that serves to tell the programmer that the method must be implemented in a child class. An interface is similar to an abstract class; indeed interfaces occupy the same namespace as classes and abstract classes. For that reason, you cannot define an interface with the same name as a class. An interface is a fully abstract class; none of its methods are implemented and instead of a class sub-classing from it, it is said to implement that interface. An interface is an empty shell. There are only the signatures of the methods, which implies that the methods do not have a body. The interface can't do anything. It's just a pattern.