Playbooks

From AWS Well Architected Framework Concepts - https://wa.aws.amazon.com/wat.concept.playbook.en.html

Enable consistent and prompt responses to failure scenarios by documenting the investigation process in playbooks. Playbooks are the predefined steps to perform to identify an issue. The results from any process step are used to determine the next steps to take until the issue is identified or escalated.

Using Playbooks

Playbooks are usually written in the language an orchestrator (Terraform) or provisioner (Ansible/Chef/Puppet) would be able to parse for automation.

Is it a software

It is like any other program that requires a runtime.