Ideal HTTP Performance
If you want to understand the essentials of HTTP2 then it is difficult to go past Mark Nottingham (chair of the HTTP Working Group). In this article he breaks things down simply with rudimentary diagrams explaining the current concepts and where things should be going.
That is, a page load should send the minimal amount of data to the server and download the minimal amount of data possible needed from it in the least possible number of round trips.
An excerpt from Ideal HTTP Performance
