A cloud availability zone is an isolated infrastructure location inside a cloud region. It is usually designed with separate power, networking, and physical facilities from other zones in the same region.
Why zones are useful
Applications can be spread across multiple zones so that one data center problem does not take down the whole service. This is a common part of high availability design.
Zones are not the same as regions
A cloud region is the larger geographic area. Availability zones are separate sites within that region.
Availability zones help teams design for real-world failures without moving workloads across the planet.