Now that you have configured the CLI, you can try it out with the following commands:
List all of the buckets you have in S3 in this account with aws s3 ls
List all of the regions where you can launch an instance with aws ec2 describe-regions
You can always type aws help to get to the manual page for a particular service and command.
Get to the manual page for EC2 with aws ec2 help
Or get to the manual page to launch an instance with aws ec2 launch-instance help
You can use the CLI on an instance or from your local machine to work with AWS services. The CLI can do (almost) anything that you can do with the console.