difference between promise vs observable

promise_observable.js

var promise = new Promise((resolve)=>{
  setTimeout(() => {
    console.log('promise timeout fired');
    resolve(42);
  }, 500);
  console.log('promise started');
});

promise.then((x) => console.log(x));

var source = Rx.observable.create((observer)=>{
  var id = setTimeout(()=>{
    console.log('observer timeout fired');
    observer.onNext(42);
  }, 1000);
  console.log('observable started');
  
  return () => {
    clearTimeout(id);
    console.log('observable disposed');
  }
});

source.forEach((x)=>{console.log(x)});

setTimeout(()=>{
  source.dispose();  
}, 500)