just that the TV commercial looks back at you through the TV and the TV follows you around everywhere, wherever you go, whatever you do, taking note of everything to get to know every single detail about you, every interest, every prejudice, every weakness of yours, to get to know you like no person, no matter how close to you does, like not even yourself do to use that information to influence you most effectively to the TV channel’s and the advertiser’s advantage, to manipulate you, to sell this information about you to other companies like insurances who use the power that this knowledge provides over you to extract every last cent of money from you, to sell you.
The Nielsen company doing surveys of a percentage of households is how they know. Nowadays they even have a tracker you wear that reports back to Nielsen what you’ve been watching/listening to based on what it can hear, in the old days it was a form folks filled out saying what they watched or listened to