HTTP/2 is a new version of the internet protocol originally developed by Google (SPDY). This plugin enables to make use of some it's optimization potential.
When enabled, resources such as scripts, stylesheets and images can be pushed to visitors together with the HTML (documentation).
Note: When using the Progressive Web App Service Worker (PWA), the service worker automatically calculates a Cache Digest based on previously pushed resources. This feature is based on the hash calculation implementation of Cache-Digest-Immutable and enables the server to only push resources that aren't already available in the client. For more information, see this article on PerfPlanet.com. It is not possible to push resources that are not used on a page. For more information, see this article