Skyrocketing in the enormous world of programming is the concept of Reactive Programming. RxJS is just one of the many implementations of this paradigm.
The way of programming we used for decades, and are still using most of the time right now, is based upon part A of a program asking for data from part B and doing something with it or just waiting to be called from another part. This is what is called as pull based programming.
Reactive Programming uses the concept of data flows. Data flowing from the same part B to part A. This is what is called as push based programming. The receiving end of the program will have to react to whatever data will be send to it in the future. This is why it’s called Reactive Programming. Reactive Programming is simply to program using, and relying on, events instead of the order of lines in the code. Usually this involves more than one event, and those events happen in a sequence over time.
This SlideShare explores the concept of Reactive Programming in brief.