Create a backlog to collect user stories. You may organize user stories in different backlogs, although it is usually more effective for agile teams to stick with only one.

Backlogs aggregate prioritized user stories. Usually it is not a good idea to work with different backlogs, since this makes it difficult to define a clearly prioritized list of topics to work on. Therefore the main purpose of the Product Backlog Doctype is to define multiple views on the work. We expect that users work with their backlog on JIRA anyway. Backlogs provide views and allow to add additional information that is relevant for a group of related units of work.