As you have seen, groups are collections of users and are applied globally. JIRA also offers another way of grouping users, which is applied on the project level only. JIRA comes with three default project roles out of the box:
Similar to users and groups, project roles are maintained by the JIRA administrator through the Project Role Browser page. There is a slight difference, however, because since project roles are specific to projects, JIRA administrators only define what roles are available in JIRA and their default members. Each project's administrators (discussed in later sections) can further define each role's membership for their own projects, overriding...