An Availability Zone(AZ) is one or more Data Centers located within a region.
The Availability Zones within the same region are connected to each other by a low latency, high bandwidth network, which makes it possible for you to provide high-availability connectivity to the internet and on-premises, and to build replicated systems in multiple availability domains for both high-availability and disaster recovery. Availability Zones are isolated from each other, fault tolerant, and very unlikely to fail simultaneously. Availability Zones do not share infrastructure such as power or cooling, or the internal Availability Zone network. So a failure at one availability Zone within a region is unlikely to impact the availability of the others within the same region
A Data Center comprises components that include switches, storage systems, servers, routers, security devices, etc. provide a means to store data and provide a path for users to access that data. They provide important services such as data storage, backup and recovery, data management and networking. Because of their high concentrations of servers, often stacked in racks that are placed in rows, data centers are sometimes referred to a Server Farms.