This infographic on online data, courtesy of TechJury, will show you how big companies that provide free service (read: social networks) get to know you better than your own parents and what they do with this knowledge. It will also help you learn more about the most common tactics used to get your data.
(Hint: if you can’t read the image below, please right-click on it and select “Open image in new tab,” then click on it to enlarge!)