What are Stat Files?⁠›››

Has anybody ever explained what these do? How useful are they?

They're CSVs you can download from the stats page on the iRacing website. How useful they are is up to how you build your theme.

You need to download the stats files from the iRacing driver info page. If you supply them in the settings, then all the data bindings starting with "stat_..." will read the data from those files.