Microsoft Sentinel’s automation rules give you the ability to develop and organize rules that can be used in a variety of scenarios, allowing you to manage automation from a central location. A playbook is a compilation of various corrective actions that may be routinely executed from Microsoft Sentinel.
When triggered by specific alerts or incidents, as determined by an analytics rule or an automation rule, a playbook can help automate and orchestrate your threat response. It can be used manually or set to run automatically in response to specific alerts or incidents.
Take a look at this video on getting started with Automation Rules & Playbooks