There is something you use every day, probably more than once, and it costs you nothing. Or at least, that's how it seems.

The map that tells you how to get there. The search engine that answers any question. The feed that scrolls. The platform where you watch videos. The app where you talk to your friends. Free. All free.

It's a fairly unusual situation, if you stop for a moment to think about it. The companies that run these services are among the largest and most profitable in history. They don't sell objects. They don't charge subscriptions — or at least, not to everyone. And yet they earn figures that would be difficult to even say out loud.

The mechanism is simple, and it isn't even a secret. These services are free for you because someone else is paying to reach you. That someone else is the brands, the shops, the companies of every kind that want to show you something while you're there. You are not the customer. You are, in a sense, the product.

That isn't necessarily a terrible thing. It's just useful to know. What has changed in recent years is the form this dynamic takes. Once, advertising was recognisable: a billboard, a commercial, a page in a newspaper marked paid advertisement. Today it is often something else. It is a video of someone telling you how much they loved a thing. It is an article explaining how to live better. It is content that looks like it came from a friend, and that was instead commissioned, planned, paid for.

It isn't necessarily a lie. That person may genuinely use that product. That article may contain useful information. But there is a difference between a recommendation and a communication strategy, and that difference tends to disappear in the way both of them present themselves. The interesting thing is not advertising itself — it has always existed, and it serves legitimate functions too. The interesting thing is how good it has become at looking like something else. At looking like a conversation, an opinion, a personal discovery.

It is worth keeping in mind. Not with systematic suspicion — that would be exhausting, and probably pointless. But with a certain quiet attention. The kind of attention that doesn't necessarily change what you do, but changes slightly how you do it.

Which is, in the end, almost everything.