I think it's metadata. Whenever you visit a website, there are many things that track you:
1. The website itself is sending your activities to ads platforms, with your hashed email address and phone number if you're signed in. It does not allow ads platform to reach you directly but email address hash is pretty pinpoint. Everyone hash the same way so it's easy for ads platform to track you across the internet.
2. The website loads trackers which monitor your activities across different websites.
That means if you search for something, not even clicking on it, it's possible for ads network to connect your search topic with your spouse.
That means if you search for something, not even clicking on it, it's possible for ads network to connect your search topic with your spouse.