When you create and launch AWS resources like an EC2 Linux instance – at the time you create the resource – you define a default region and zone that it will run in.
Regions are large areas of coverage related to geographic regions around the world. Zones exist within regions.
For example at the time of this writing AWS (Amazon Web Services) provides four US Regions, US West N. California, US West Oregon, US East Ohio, US East N. Virginia.
AWS provides redundant end-points to access these regions via at least two tier one internet providers per region.
Each regions contains two or more zones (also known as Availability Zones). For example, US West N. California currently contains zones us-west-1a and us-west-1c.
References:
https://docs.aws.amazon.com/AWSEC2/latest/UserGuide/using-regions-availability-zones.html