What is "use.typekit.net" doing in the header of a page?

//use.typekit.net/txx2jfv.js is the script including in the header of page..this file contain some jquery code...The use of that code is to use beautiful FONTS on your page...check the site https://typekit.com/

Typekit is a provider of webfonts. They probably are the only service that benefits from having the script in the head, because it blocks rendering while the fonts download, thus preventing a FOUT (flash of unstyled text)

The script works by fetching some css files that contain the fonts in base64 encoding.