Confusing term Interactors in Clean Architecture

An Interactor is a design pattern that has nothing to do with "business logic" concept. Without going in deeper level of detail the Interactor pattern is an extension of the Command pattern; Each "business logic" object is treated as a "black box", a simple instruction to be executed for the client, decoupling the object that invokes the operation from the one that knows how to perform it. (refer to the bibliography for extended explanation).

In the android enviroment there is a simple 'rule' that demands to the programmer to do long time consuming task in a background thread, so the interactor patterns extends the "Command pattern" adding a layer of threading. All this complex stuff is implemented to create a "clean architecture" which entails a code that is scalable, maintainable and (arguably) understandable.

About the question .. ¿what is the design pattern for layer-layer interaction? It could have more than one rigth answer, depends of the situation. You could use a simple Interface as the entry point, so you could use the Adapter pattern, or maybe the Facade pattern, or if you want to do something more advanced you could implement an eventbus system.

Source: Design patterns explained simply - auth Alexander Shvets. page 14 (Adapter), page 32 (Command), page 47 (Facade)

In the clean architecture approach, the Use Case Interactor is a layer that express the specific business rules. The Use Case Interactor interacts with the Entities (agnostic business rules) to achieve the Use Case intention. Entities can be used in another applications, once they are agnostics, on the other hand, the Use Case Interactors are specific application objects.

Can be found in the Clean Architecture book by Robert C. Martin at chapter 20