What's the difference between a Contract in Laravel and an Interface in PHP?

As far as I can tell, Laravel refers to the interfaces it extends as Contracts because they are used by Laravel. But this seems a bit like circular reasoning. There is no value added in changing the terminology of an existing PHP feature simply because your project uses it.

Is there something more to it? What's the logic behind coining a new term for something that's a standard PHP feature? Or is there some feature of Contracts that are not already in Interfaces?

via Chebli Mohamed