How to find your regions and Availability Zones using the Amazon EC2 CLI?

Use the ec2-describe-regions command as follows to describe your regions.
PROMPT> ec2-describe-regions
REGION us-east-1  ec2.us-east-1.amazonaws.com
REGION  ap-northeast-1  ec2.ap-northeast-1.amazonaws.com
REGION  ap-southeast-1  ec2.ap-southeast-1.amazonaws.com