Update on April 02, 2021
HTTP is the Hypertext Transfer Protocol, it allows the transfer of information over the internet, HTTP2 is the first update and improves the performance of the sites. HTTP needs several lines to load elements, it finishes loading one request and begins loading the other, these lines are known as TCP connections; nowadays hundreds of requests are loaded on a website resulting in slow page load time. HTTP2 handles multiplexing and that means that within TCP connections it includes multiple requests and prevents repeated data from being sent to achieve lower latency.
This version gives priority when transmitting elements from the server to the browser, loading HTML code first, then CSS code (styles) and finally programming codes such as .js, .php, .py, among others. HTTP2 improves the speed of websites but not all, when you have an optimized website and HTTP2 is used you will not notice the difference and the way to know if a website uses the protocol is through browser extensions such as:
Or through the browser's inspection tool and for this you must right-click and select inspect.
Next, locate the Network tab and the protocol used is shown in the protocol column.
If you want to implement HTTP2 it is necessary to have an SSL certificate on the website as it works better.