the.com/tracker

means A tool or piece of code that follows and records what you do — where you go, what you click, how long you linger — so someone else can build a profile of your behavior.

from From 'track,' rooted in the idea of following footprints or a trail left in the ground — hunters and scouts 'tracked' game long before anyone imagined digital trails. The '-er' turns the verb into 'the one who does the following.' By the 20th century 'tracking' extended to radar, shipments, and eventually software that follows your clicks the way a hound follows a scent — the wilderness metaphor never really left, it just moved indoors.