What does this tool do?

H5P packages are not innately 'runnable' - they are intended to be served from a LMS or some sort of platform that hosts all the neccesary scripts and fonts and so on that are also required to show the content. So unless you know how to host and serve those files, you're generally out of luck. That is, unless you can package all the required scripts and files into a package which you can host independently.

TL;DR Turn your .h5p file into something that you can then run on any static web site.

Choose your h5p file

Then what?

Extract your zip file to web server (it won't run locally) and open the index.html file.