AWS Region is a distinct geographical location, completely isolated that is located far from each other. Regions have the highest fault tolerance. As of 2018, AWS has 19 regions established throughout the world. However, When you create an account, it determines which regions are available to you.
Amazon resources created in one region are specific to that region and are not replicated to other regions. For example – Amazon EC2 instances created in one region remain in that region and cannot be transferred to another region. Instead, you can copy the Machine Image and launch a new instance in another region.
Availability Zone –
Each Region provides multiple physically separated, low latency, high throughput Availability Zones(AZ). These AZ let users launch resources which provide fault tolerance and high availability. As of 2018, AWS has 57 Availability Zones throughout the world across 19 regions. When resources are launched in a particular region, you have the option to specify the AZ. However, if you don’t choose the AZ, then Amazon will choose one for you. There are certain limits on how many resources can be launched by a customer in an AZ as the Availability Zone grows over time.
Edge Location –
An Edge Location is where the users actually access the services. These Edge locations are present in some of the major cities across the globe to reduce the high latency. As of 2018, there are about 144 edge locations used the Amazon Content Delivery Network, called the CloudFront. Without these Edge locations fetching resources/content of websites on the other end of the world(say the USA) will take longer time for a user in the opposite end of the world(say, Asia).
Amazon constantly adds new AWS Regions, Availability Zones and, edge locations to expand its global infrastructure. You can click here to refer the current information on these.