For the non-technical people: this basically that when you visit a website with this kind of tracking, the website is kind of making it look like the trackers are coming from them instead of from the tracker network.
Traditional adblockers rely on domain filtering (ie.: based on the website you are visiting)
Non-technical explanation
When you visit website X.com if it has a tracker from Y.com, your computer would then let Y.com know you visited that website and a couple of other information without you knowing.
Adblockers generally have a list of tracking / ads websites (where Y.com would be included). Thus that tracker would get blocked.
With this new technique, the website X.com instead of having Y.com inside of it, it now has Y.X.com and so your blocker things it’s coming from X.com and so it doesn’t block it.
Or at least this is my understanding of the technique. Thoughts are appreciated