As of 2021 AWS consists of 25 Regions and 80 Availability Zones (AZ). There are 6 more Regions and 18 AZs planned for the foreseeable future.
Availability Zone
AZs are isolated locations within data centre regions from which cloud services originate and operate. Just imagine a massive warehouse full of servers.
A single AZ can consist of multiple data centres.
AWS Region
Regions are geographic locations in which AWS data centers reside. Each region consists of two or more AZs.
Edge Location (EL)
Apart from Regions and Zones there are also Edge Locations. These are smaller setups in different locations in order to provide the biggest coverage possible for low latency access.
ELs serve cached content so that the user doesn’t always have to send requests to Data Centres that could be far away and thus increasing latency. This typically consists of Cloudfront which is Amazon’s CDN.
There are over 220 edge locations at the time of writing so much more than there are regions.
The way this works is that when someone from the US wants to download a file from S3 that’s in a bucket in Australia, first they’d have to download it directly from Australian data centre but every other time it will come from the Edge Location nearest to that user.