What is RxJS?
RxJS is responsible for the reactivity in Angular
RXJS is not part of angular but it is an external Library which useful in reactive programming, in which using observable we can do asynchronous tasks
It's an external library so we can use it with any programming like jquery.
Angular provides by default installation of rxjs, so no need to install it.
What is Reactive programming?
Reactive Programming is a programming paradigm wherein code is written to react to events that are produced from a data source or event emitter, such as a mouse click.