Using RxJS, you can represent multiple asynchronous data streams (that come from diverse sources, e.g., stock quote, tweets, computer events, web service requests, etc.), and subscribe to the event stream using the Observer object. The Observable notifies the subscribed Observer instance whenever an event occurs.
Because observable sequences are data streams, you can query them using standard query operators implemented by the Observable type. Thus you can filter, project, aggregate, compose and perform time-based operations on multiple events easily by using these operators. In addition, there are a number of other reactive stream specific operators that allow powerful queries to be written. Cancellation, exceptions, and synchronization are also handled gracefully by using the methods on the Observable object.