How does lead generation work?

From my understanding a lead gen business is a business that pretends to be an actual business and is paid by legitimate businesses in the area to reroute calls from customers to them. What does a lead gen site look like? How can you write an about page or services page without lying? How do you get listed on GMB if there's no address? Is it just a landing page with a call to action? Or have I misunderstood what lead gen means? Can someone link to some examples of these types of sites