Much more than a Sim. A WhatSim

"With just €10 you can chat for free and without limits anywhere in the world for a year. And you can do it for always for just €10 a year. WhatSim has neither fixed costs nor monthly payments and it never expires."

How can €10/year be free? Also, no monthly payments -- but there are still yearly payments.

So it follows that one would need a phone to use exclusively for WhatsApp, no voice, no nothing else?

Also, do I understand correctly, this only works with public commercial WiFi networks (ex Starbucks) instead of mobile networks?