How does the Facebook pixel detect a user who has clicked from an ad?

Question

Facebook

I can’t understand the algorithm for sending requests by the Pixel facebook script to the user who went to the site, according to his user data (who he is on Facebook or Instagram, that is, his id can be his, interests for subsequent retargeting when creating a custom audience according to users from Pixel facebook). How will he determine the user who went to the site, did he go there from an advertising publication or just from a search engine?
I explain: we installed the script, wrote some requests into it that take information from the user's browser (I don’t understand how this happens). How will the script understand what kind of user it is, how will it identify this user later, will it find it during retargeting, that is, when setting up an audience based on data for sending repeated advertising? How does a pixel remember users in general (maybe it marks it somehow)?
I understand why events with parameters are needed, the person went to the form with the event, the script reports to Facebook, and Facebook to some kind of data storage for your advertising account. How will a pixel located on the site be able to understand that this is exactly the user from the advertisement? Maybe, during the transition, Facebook somehow marks the user with some parameter, and then the pixel, by this parameter, recognizes and endows it with events that it made on the site and then sends it all back? In general, I'm confused, please explain this algorithm to me.

Answer 1

Through cookies. Here is what they say about cookies

Answer 2

HERE I READ, and came to the conclusion, SAY WHETHER THIS IS OR NO, I VERY FORGET TO TAKE TIME, THE QUESTION DOES NOT ALLOW SLEEP DIRECTLY I DON'T KNOW
the principle of the script itself, how it is activated at all, how it sends the form, for example, we place the main pixel in head
how does it read that exactly the person who got to my site switched from an advertisement, let's say that when the transition is made, a person is already sitting with cookies installed for him, and what kind of cookies, date of birth, age ??? what does he generally read and how, and there is also an event pixel and there is not one of them on Facebook, that is, which we can place, aimed at sending a form about the user's action, whether it's a purchase or just viewing, but how he understands and directs this form, more precisely, how the main pixel understands by accepting forms from events they can be 10 pieces of these pixel events, that this is the same user, but the main pixel of the cookie was counted at the beginning, and it turns out that he passed his cookies to the data marked as a serial number to the user himself when walking around the site through these events can ???,and in the future, the event script sends the form with this serial number to the main pixel for this user, and after accepting it, it sends it to your Facebook account data, so???? I really need help if it’s not difficult to explain to me ....