Google makes billions of dollars in revenue each fiscal quarter. That money comes about by the same process that all companies use: They sell a product to their customers. Their customers pay money for that product.
Who’s Google’s customer? You? Really? When’s the last time you paid Google for anything?
Advertisers are Google’s customer. What do they sell to advertisers? They sell you. Or, at least, they rent you out, or provide access to you.