Amazon EC2 allows placement of instances in multiple locations. Your instance can be placed in a region, which corresponds roughly to a physical location or area, such as US East (N. Virginia), Canada (Central), EU (Ireland), and so forth. There are numerous options to choose from. Alternatively, it can be placed in an Availability Zone, which is essentially a logical grouping of servers or racks of servers separated into an artificial ‘location’ within a given region. Instances paired across Availability Zones are isolated from failures in other Zones, ensuring redundancy in case of large-scale failures.
For more information on Regions and Availability Zones, go to: