Even though Observable and Subscriber alone make it possible to implement a lot of workflows, the whole power of RxJava is hidden in its operators. Operators are used for tweaking elements of the stream or changing the stream structure itself. RxJava provides a huge amount of operators for almost every potential scenario, but it is out of the scope of this book to study all of them. Let's now look at the most used and foundational operators; most others are just a combination of the basic ones.