When creating a display, you have two options: test mode or live mode. There is no difference in functionality, both function exactly the same. The difference is cost and how long the display can be active.
Cost
A test display is free to use, you will not be charged for it. A live display will be billed monthly.
How long the display can be active
A test display is active for 30 minutes: after this time the player will not receive any more updates from Lumicast, and its screen will be turned off. A live display can run 24/7.