How does facebook pixel knows which conversion came from which facebook ad?

Question

I was going through facebook pixel and was a lot confused about how does facebook pixel knows which conversion came from which facebook ad ?

Suppose i have this url http://example.com with facebook pixel installed and i have posted two ads on facebook namely Ad1 and Ad2. Users clicks on some ad and land on my url page.

So how does pixel tell facebook that that particular user came from which ad ? and does the pixel even get into such detail ?

And also, does a pixel fire whenever a user lands on above mentioned url or only when the user came from a facebook ad ?

Answer 1

1. Facebook knows which facebook users were exposed to ads and provided that same user has been using Facebook in that same browser, they can attribute the pixel fire back to that user.
2. The pixel should fire for all page loads not just those for when people visit from a Facebook ad.
3. If there are multiple ads that a user was exposed to, Facebook would give credit to the ad that was most recent.