A zone is an individual area within a location. To play music, your location needs at least one zone. For example, one hotel may have three zones - a bar, lobby and restaurant. Each zone that is created allows for a unique stream of music and will add an extra cost to your subscription.
Learn how to add a zone here.
Each zone needs to be connected to a player. A player can only connect to one zone at a time.
Find your player here.