What services allow you to track a person using an advertising ID?

Question

contextual advertising

Good afternoon!
Interested in the answer to the question, or a more detailed explanation of my assumptions.
As you know, many sites use traffic analytics systems, advertising services, etc. I do not know all the names of such technologies (I will be glad to receive the whole list). So. There are also sites that show statistical data of such analytics, including those that allow you to get the relationship between sites through tracking identifiers, incl. advertising identifiers. The question arises - how easy and how to calculate specific users walking on certain sites by their track identifiers.
Where did the question come from:
1. many services use (purchase) this information to more accurately suggest the preferences of specific users, according to their list of visited sites, search queries, etc., respectively, if the user has registered at least one of the thousands of visited sites, then by relationships through its identifier, it can be easily linked to other sites. As a result, already knowing a person, with his email, phone, you can learn a lot about a particular person, I don’t even have access to the confidential information of each visited site.
2. sometimes, just by visiting some sites, after a few minutes / seconds, a letter or even an email from this site with a specific offer arrives, this once again confirms point 1, i.e. the site calculated by the identifier where I still went for some period, checks on these sites in public places the presence of my contacts, or at least one, then makes a paid request somewhere else where more or less accurate contacts give more complete information about you, which analyzes the robot and sends the formed offer to the received contacts.
Is it really all possible as I described, and what services offer such information and at what prices, is it even free to some extent? I just want to understand how to defend all this, because. these trackings together make it possible to identify any person, including using this information for illegal purposes, and sell this information, possibly for a penny, to everyone.
Or the second option, tracking really gets the whole picture of the visits of a particular user but do not have access to obtaining identifying data? Those. services know that you like this or that, but do not know your identifying data. And there are services that illegally receive / transmit your information from / from other services, violating the requirements of anonymity of the information collected. Is it so?