Explanation
Each Region is completely independent. Each Availability Zone is isolated, but the Availability Zones in a Region are connected through low-latency links. A Local Zone is an AWS infrastructure deployment that places select services closer to your end users. A Local Zone is an extension of a Region that is in a different location from your Region. It provides a high-bandwidth backbone to the AWS infrastructure and is ideal for latency-sensitive applications, for example machine learning.
Reference: https://docs.aws.amazon.com/AWSEC2/latest/UserGuide/using-regions-availability-zones.html