Observable is not part of Angular but RxJS. RxJS is installed together with Angular.
Promise is part of ES2015.
Promise pretty much serve the same purpose, which is for asynchronous operation, such as return response from an asynchronous call.
|1||Handle multiple events at a time||Handles a single event at a time|
|2||Cancel-able & Retry-able||Neither can be cancelled nor retried|
|3||Supports map, filter, reduce and similar operators||–|