This is a draft article likely to evolve or be deleted or merged with another article in the future.

General concepts

• Observer: when subscribing, get all past emitted values
• Subject: when subscribing, get only next-to-come emitted values
• BehaviorSubject: like Subject but keeps a current state, which is the last received value or the one passed to the constructor if none received, then emits it immediately when being subscribed to
• ReplaySubject: when subscribing, get all last X emitted values
• AsyncSubject: emits the result of an asynchronous operation when the observable completes

Misc

• shareReplay: when subscribing, emits the last value. This helps avoid making a new HTTP request for each new subscription, for instance.

Resources

• RxJS Les clefs pour comprendre les observables (T. Chatel)
• RxViz - Animated playground for Rx Observables
• RxMarbles: Interactive diagrams of Rx Observables
• The introduction to Reactive Programming you've been missing