What is the name of a business model where you offer a product for free to entice people to use your service? I'm not referring to freemium. I am more talking about how Google works. They offer gmail, youtube, etc for free to encourage more people to use the Internet, and in return they get more people clicking on their AdWord ads.
So that actual product you give away is not for sale, even for a premium. It is just a means to encourage people to use your other offerings.
For example: If Apple made an accounting application for the iPad which was free. Their business is not accounting but instead trying to get more accountants to buy iPads.
Where can I find more information about this?