Zone Redundancy in Azure

Azure services that support availability zones fall into three categories:

• Zonal services: Resources can be pinned to a specific zone. For example, virtual machines, managed disks, or standard IP addresses can be pinned to a specific zone, which allows for increased resilience by having one or more instances of resources spread across zones.
• Zone-redundant services: Resources are replicated or distributed across zones automatically. Azure replicates the data across three zones so that a zone failure doesn't impact its availability.
• Non-regional services: Services are always available from Azure geographies and are resilient to zone-wide outages and region-wide outages.
  ^[1]