A physical zone, or just zone, is an organisational unit that contains nodes where each node is in one, and only one, zone. Later, while in production, a node can be taken (allocated) from a specific zone (or not from a specific zone). Since zones, by nature, are custom-designed (except for the ‘default’ zone), they provide more flexibility than a similar feature offered by a public cloud service (ex: availability zones).
Some prime examples of zone usage include fault-tolerance, service performance, and power management.
A newly installed MAAS comes with a default zone which contains all nodes unless you create a new zone. You can therefore safely ignore the entire concept if you’re not interested in leveraging zones.
You cannot remove the ‘default’ zone or change its name.