"Pixels (aka web beacons/web bugs/java script). Pixels are tiny graphics with a unique identifier that are used to track the online movements of web users. Unlike cookies, which are stored on a computer’s hard drive, pixels are small graphics that are about the size of the period at the end of the sentence that are embedded invisibly on web pages or in HTML-based emails. Our third-party analytics providers may place pixels on the Site that track what other websites you visit (both before and after visiting the Site). Our third-party analytics providers use information obtained from pixels to help us improve our business and the Site. We do not control the use of pixels by third parties. See the section on “Third party analytics providers” below."
-https://www.gatesnotes.com/Privacy-policy
Among other things, uBlock Origin blocks resources that the developers and filter list maintainers consider privacy risks, of which "pixels" are a subset.