Dev Tools have had an overhaul (in Chrome Canary for now) and it’s now should be considered an invaluable tool on its own (if it wasn’t already before). The Audits tool is now being powered by lighthouse which provides a series of tests for measuring the quality of your site, specifically around PWA-ness, performance and accessibility. Have a look at this article and associated video for the full scoop.
The scores at the top for Progressive Web App, Performance, Accessibility, and Best Practices are your aggregate scores for each of those categories. The rest of the report is a breakdown of each of the tests that determined your scores. Improve the quality of your web page by fixing the failing tests.
Lighthouse is an open-source project. To learn lots more about how it works and how to contribute to it, check out the Lighthouse talk from Google I/O ’17An excerpt from What’s New In DevTools (Chrome 60)