Via Android Central:
This is the interesting part. Google does use your data to make money. A lot of money. Scrooge McDuck swimming in a pool filled with gold coins level money. But not by selling it off.
Instead, Google offers a tailored service to the people buying ad space. Let’s say I make a product that appeals to people who like to go fishing. I want everyone to know about my product, but my research shows that people who like to go fishing are more likely to spend money and buy my product. Having the people who like to go fishing see my ads is really important to me.
This is an important thing for people to keep in mind whenever they’re putting their personal information into anything online, with Google or otherwise.