What is the difference between an 'Abstraction' and a 'Facade'?
Is there a difference at all? Or are the terms interchangeable?
The facade pattern is an simplified interface to a larger, possibly more complex code base. The code base may be a single class, or more. The facade just gives you a simple interface to it.
Abstraction, is used to represent a concept, but not to be bound to any specific instance. (Ie: An abstract class). This doesn't imply simplifying (like the facade pattern does), but rather making a 'common' interface or representation.
Facade is a specific design pattern, meant to hide the internal stuff inside a package / module from its clients behind a well-defined interface. It usually hides several interfaces/classes behind a single common one, hence its name.
'Abstraction' is a general term, meaning to hide the concrete details of something from the outside world.
So these two are not interchangeable terms.
Facade is a GoF design pattern, very specific. In essense, it's about hiding over-complex functionality from the main body of your application.
Abstraction is a more vague term related to hiding functionality of a service from its client.
Abstract to me means taking the common parts of a collection of things and creating a base thing from them, which the collection can then draw on, sort of like a parent class.
A façade is a face (literally speaking), so they analogy of a base class doesn't quite hold. A façade is more of an interface, so it wouldn't have to be related to the things that use it. I think of it more like a mask. My class will have a "disposable" mask, for example.
So the difference, in my mind, is that an abstract pattern allows a hierarchy to be built, where as a façade pattern allows classes look similar.
来源：https://stackoverflow.com/questions/2288643/what-is-the-difference-between-an-abstraction-and-a-facade