Collection operators will accumulate all emissions into a collection such as a list or map and then emit that entire collection as a single emission. Collection operators are another form of reducing operators since they consolidate emissions into a single one. We will cover them separately since they are a significant category on their own, though.
Note that you should avoid reducing emissions into collections for the sake of it. It can undermine the benefits of reactive programming where items are processed in a beginning-to-end, one-at-a-time sequence. You only want to consolidate emissions into collections when you are logically grouping them in some way.
