Fast Pageload uses preloading to make your browsing experience feel more fluent and the web overall faster. This is archived by just in time preloading pages your are quite likely to visit. Studies show, that when you hover over a link there is a 50% chance that you will click it. Faster Pageload starts loading the page when you hover and thereby when you actually click (on average 400ms later) the page is already loaded to a big portion. There is no technical effect, as the pages are still loaded normally but for your as human it will feel faster, as the pages builds up instantly after you clicked.
For further speed improvements we lazy load images on the web pages. So only the images you really see are loaded.
Give it a go and feel the magic.
Credits: Addon Icon by Freepik (https://www.flaticon.com/authors/freepik) Instant.page script that does the actual preloading is by Alexandre Dieulot (https://dieulot.fr/) and licensed under the MIT license (https://opensource.org/licenses/MIT)