Correct page rendering is critical to succeed in SEO. Surfer gives you access to screenshots from the Google bot perspective. You will be able to learn how the first 50 page results are seen by Google.
If you would like to see how your or your competitors' pages are rendered, choose "full" analysis. It will take 10-20 seconds longer to load the query as Surfer need to scrape additional data.
Learn more about screenshots and rendering: