Difference between callback and interface

What is the difference between these two piece of code

 btn.setOnClickListener(new View.OnClickListener() {
        @Override
        public void onClick(View v) {

        }
    });

is that inner interface of View class, if so we know that interface can not be instantiated

And here

soInterface.getAnswers().enqueue(new Callback<SOAnswersResponse>() {
      @Override
      public void onResponse(Call<SOAnswersResponse> call, retrofit2.Response<SOAnswersResponse> response) {

      }

      @Override
      public void onFailure(Call<SOAnswersResponse> call, Throwable t) {

      }
  });

its callback that it required in the enqueue method, what this syntax define, is it interface "CallBack<>" defined some where and we are calling it here as inline interface, but again interface can not be instantiated like callback syntax says "new CallBack(){}"