HTTP/2 is the newest version of HTTP protocol released in 2015. HTTP/2 got many features and performance advantage to make website resources load faster.
HTTP/2 is capable of loading multiple page elements in parallel over single TCP connection. It reduces the latency to serve requested content faster by doing the following.
There is no concrete answer as it depends on client network speed, browser and many other factors. AKAMAI and Coudflare has demo site where you can experience latency and how fast it loads over HTTP/2 vs HTTP1.1
Since launch, HTTP/2 is already used on more than 14% of all websites.
HTTP/2 Implementation is quite straightforward and this can be configured in web servers, network devices, CDN.
Once you are done with the implementation, use this tool to find out if HTTP/2 is enabled or not.