First, let's remind that an Observable publishes values only when we subscribe to it.
So to subscribe to such stream, you have to invoke its subscribe() method, and we parse to it an observer.
Usually we do not pass the observer but a command line:
It is a coding shortcut.
ððĻ, ððĄð ðŽðŪððŽððŦðĒðð ðĶðððĄðĻð ðĒðŽ ð ðĶðððĄðĻð ðĻð ðððŽððŦðŊðððĨððŽ, ð°ðĄðĒððĄ ðððĪððŽ ðð§ ðððŽððŦðŊððŦ ððŽ ðĐððŦððĶ ðð§ð ððððĨðŽ ð°ðĒððĄ ððĒððððŦðð§ð ð§ðĻððĒððĒððððĒðĻð§ðŽ ðŦððððĒðŊðð ððē ððĄð ðŽððŦðððĶ.