Difference between Call and Observable Response in Retrofit interface

Question

I don't understand meaning 2 way this (Observable and Call.)

@GET("/users")
fun getAll(): Observable<List<User>>

@GET("/users")
fun getById(): Call<List<User>>

I want to understand it, please. Very Thanks.

Answer 1

If you are using retrofit without RxJava you can use call. If you are using RxJava you should use Observable.