@Openmind, it's... complicated but easy.
What's the difference with AMP pages? when you visit Google and search something and your site appears on the results, then Google sees you are AMP compliant and then when you click on your result, your page loads like magic, why? because there is a preloading. Your content is being cached/preloaded (any of both) and served from the location nearest to you, then you hit your site but some or all of your stuff was already loded. Bing introduced AMP support, Yahoo did too.
So, it's like someone visiting your site from zero, directly, the browser loads everything from scratch every time. This unless that someone visited the site previously so browser cache enters the game, there you can also play and optimize for cache (via htaccess, meta tags, etc) and make your site load faster, why? because that person already cached some elements in their browser. Ok, when it comes to Google search results, it's like that someone had a friend giving them a copy of your site so when they get to you they already have some elements int their browser, Google is that "friend" giving that copy. Bing and Yahoo can do this too. CloudFlare entered the game and somehow you can be served some cached content too. Tried my best to explain how it works, I too got caught at the beginning into thinking it as a faster format, it's not exactly that. It was bult for preload and cache but not on your browser, instead somewhere else.