What is it?
It's a script that renames all your EBS volumes to the name+device of the EC2 instance they're attached to. It also applies the "environment" tag to each volume, read from the instance. (I use the 'environment' tag in billing reports.)
So if your instance's "Name" tag is backend-1234.prod.example.com and the volume is mapped to /dev/sdh, this script would apply the tag
Name=backend-1234-prod-example-com-dev-sdh to the volume, and set the environment tag to match the instance's.