What is Observable

In simple term, Observable is a stream of data.
In Rxjs,Mostly they use Observable for reactive programming.
How to create Observable in simple way?
import {Observable} from the 'rxjs'
var testobservable = Observable.Create((Observer:any)=>{
Observer.next('Hello');
Observer.next('AngularWorld');
});
Explanation of above code in simple way :
Observer is stream of events which sends notifications to Observables.
There are 3 Types of notifications are send through Observers.
1) Next
2) Error
3) Complete
The above notifications should be subscribed then only it will display in browser.
testobservable.subscribe((x:any)=>console.log(x))
Now you see 'Hello Angularworld' output in your browser console tab.