https://www.cnet.com/news/heres-how-apples-browsing-privacy-features-will-work-safari/

At its Worldwide Developers Conference earlier this week, Apple said it would help prevent shadowy web trackers from following you from website to website as you browse on Safari, the consumer electronics giant's own web browser. It will also prevent them from tracking you between different browsing sessions, which they can do even when you're using Safari's private browsing mode.

If you're asking yourself whether web-tracking tools can really do that, the answer is yeah, they can.