Observable

In reactive-programming, observable are things that Observer subscribes to

Hot, Cold and Connectable observable

• Hot: immediately begin to emit the item as soon as it's created.
  • The observer that subscribe to this observable may start observing the sequence somewhere in middle
• Cold: wait for the observer to subscribe to it before emitting the items
  • These observer are guaranteed to see the item from the beginning.
• Connectable observer: these observers does not begin to emits item until its Connect method is called weather or not you have any observers subscribe to it.

[!note]
Observable doesn't support BackPressure. For BackPressure support, use Flowable