What is the difference between an interface and abstract class?

Question

What exactly is the difference between an interface and abstract class?

Answer 1

To give a simple but clear answer, it helps to set the context : you use both when you do not want to provide full implementations.

The main difference then is an interface has no implementation at all (only methods without a body) while abstract classes can have members and methods with a body as well, i.e. can be partially implemented.