Power Apps Checker was first introduced as the Solution Checker in the new Maker Experience for Microsoft Dynamics 365 and the Common Data Service.
We also got the App Checker for Canvas Apps, and the Flow Checker for flows.
Now they are all combined under the same umbrella - the Power Apps Checker!
Read all about it in the documentation.
Microsoft also provide us with an API to invoke the checks. This allows for automation in CI/CD pipelines, and for any tool or code to consume - which is exactly what this tool does!