Those are browser definition files, which are used by ASP.NET WebForms applications:
How to detect browsers in ASP.NET with browser files
ASP.NET Web Server Controls and Browser Capabilities | Microsoft Docs
If your computer is running any WebForms applications which haven't been configured to assume that all requests are from "up-level" browsers, they will likely stop working as intended.
Modern web applications should avoid trying to detect the browser, and instead rely on feature detection:
Implementing feature detection - Learn web development | MDN
But as Griff said, randomly deleting files and folders when you don't understand what they are is a very bad idea.