What is ReactiveX?

ReactiveX is a library for composing asynchronous and event-based programs by using observable sequences. It extends the observer pattern to support sequences of data and/or events and adds operators that allow you to compose sequences together declaratively while abstracting away concerns about threading, synchronization, concurrency, data structures, and low-level API complexities. It is commonly used for handling user interface events, processing data streams, and building responsive applications.