In Appspace, Channels are the mechanism by which the content that you upload gets connected to your displays.
Channels can be published to multiple displays - although infrequently used, displays can have multiple channels assigned.
NOTE: During your department's onboarding to Appspace, you were set up with a basic Fullscreen Playlist channel, and your content was assigned to it, and it to your display. However, that is not the limit as far as customizing your signage goes. You may have more than one channel if you need different content to go to different displays.