An Epic is a large chunk of work, a large feature which needs to be divided into small User Stories. An Epic can span over one or multiple Sprints and is not complete until all its associated stories are completed. An Epic usually contains 5-10 User Stories.
A large feature, that is implemented by multiple development teams can be handled by creating Global Epic. It can have User Stories which are part of different projects.
To plan a feature that will be developed and maintained by one team, use Project level Epic.
You can use Epic Board to plan both project level and global epics. Epic progress status depends on the status of its underlying user stories.
To track the progress of epics user stories in a sprint or release, use available “Epic User Story” swimlane in respective board. User Stories will be shown under available epic names. All user stories, which are not linked to an epic, will be shown under “no epic” swimlane category.