The script solves the privacy issue with Google fonts, e.g. there are no longer IP addresses transmitted to Google servers in the USA (the transmission without explicit opt-in is not GDPR compliant).
In short, the direct link to Google Fonts just has to be replaced with a few lines of code and has to be removed from the template's css files (if necessary).
The script will then place copies of the font files in the template directory and generate the needed CSS files and their calls.
For more information please read the readme file which is included in the download.
The downloadable zip is NOT a module installer, it has to be unzipped locally and the script files have to be copied into the font directory via FTP.