HTTP/2 is a major revision of the HTTP network protocol used by the World Wide Web. It was derived from the earlier experimental SPDY protocol, originally developed by Google. HTTP/2 was developed by the Hypertext Transfer Protocol working group httpbis of the Internet Engineering Task Force.
HTTP/2 increases performance, speed and security of the websites. You can find out more about this feature here
This test can check both HTTP and HTTPS. However, as most browsers only support HTTP/2 for HTTPS, you should first implement HTTPS if you’d like to benefit from the advantages.