A case holds everything for one matter: the files, the timeline, the tags and the markup. Begin by creating a new case or importing one from Timeline Presenter.
When you create a case you choose where it lives. A case synced with the cloud is stored in the app on each of your devices and kept in sync, so it opens on your Windows PC, Mac and iPad alike and can be shared with colleagues. A case stored in a local folder stays on one device and is never uploaded. See Cloud Cases and Sync and Share a Case and Collaborate.
Cases are listed on the main page of the app. See Open Case for the ways to open one, and Case properties under Create New Case for the case name, case number and cover image.