So far, we have had a look at some operators that will let you create streams or change streams with the map() and filter() operators, we have learned how to manage different AJAX scenarios, and so on. The basics are there, but we haven't really approached the topic of operators in a structured way. What do we mean by that? Well, operators can be thought of as belonging to different categories. The number of operators at our disposal is a staggering 60 plus. It's going to take us time to learn all that, if we ever do. Here is the thing though: we just need to know which different types of operators exist so that we can apply them where appropriate. This reduces our cognitive load and our memory. Once we know which categories we have, we just have to drill down, and most likely we will end up knowing 10-15 operators in total and the rest we can just look up when we need them. 

Currently, we have the following categories:

• Creation operators: These operators help us create streams in the first place. Almost anything can be converted into a stream with the help of these operators.
• Combination operators: These operators help us combine values as well as streams.
• Mathematical operators: These operators perform mathematical evaluations on the values being emitted.
• Time-based operators: These operators change at which speed values are emitted.
• Grouping operators: The idea with these operators is to operate on a group of values rather than individual ones.