In an SDDC, availability zones are collections of infrastructure components. Availability zones are isolated from each other to prevent the propagation of failure or outage across the data center. Use regions to place workloads closer to your customers, comply with data privacy laws and restrictions, and support disaster recovery solutions for the entire SDDC. 

This design uses a protected region (Region A) for SDDC management components with one or two availability zones and recovery region (Region B) with a single availability zone. You can place workloads in each availability zone and region. Usually, multiple availability zones form a single region.

This VMware Validated Design uses two regions, with the option to use one or two availability zones in Region A and single availability zone in Region B. You can expand the design to include multiple availability zones.

Figure 1. Availability Zones and Regions
Availability zones provide isolation of infrastructure components if failure occurs. Regions consist of one or more availability zones. Use multiple regions for disaster recovery.