Explain the Interfaces in Ruby

Recall that in object-oriented programming, an interface is a collection of abstract operations that cannot be instantiated. Even though Ruby is object-oriented, it doesn't have interfaces. Interface-like classes can be constructed in Ruby by creating classes whose operations have empty bodies. These pseudo-interface classes can be used as super-classes of classes which implement the interface. Pseudo-interface classes can still be instantiated and their operations can still be known as without overriding them, so they are only a bit like real interfaces. One way to make them more like interfaces, though, is to implement the operations in pseudo-interface so that they raise exceptions if they are called. This forces sub-classes to override the operations in these pseudo-interface classes before they can be used.