The feature is called "Google Signals." Here are documentation links to how it's use in Google Ads & Google Analytics.

Ads: https://support.google.com/ads/answer/2662856#zippy=,when-yo...

Analytics: https://support.google.com/analytics/answer/9445345?hl=en&re...

tl;dr If logged in to Chrome, your Google Account can be used as an "identity signal" in place of a first-party cookie. This allows cross-domain and cross-device tracking.