AMI stands for Amazon Machine Images, which is an Amazon EC2.
An AMI in AWS is a template that includes software configurations and helps build virtual servers within the AWS environment.
Two types of AMI are available: EBS - backed Instances and Instance Store - backed Instances.
Yes, AMI is region specific as it generally contains software configurations. But if you want to share it with another region, you need to copy the AMI to that region, and then you can share it.
The minimum length of an AWS AMI ID is 1, and its maximum size is 1024.