The main revenue stream of social media companies such as Facebook and Twitter is targeted advertising. Targeted ads are created and/or displayed to reach specific users based on the data they (knowingly or unknowingly) provide on social media platforms. Different types of information can be taken into account, including demographics (age, gender, relationship etc..), location (based on the location explicitly given by users or through their IP address), and interests (i.e: “likes”).

Other tech companies whose focus is not social media (i.e: Google and Dropbox) also sell the personal information of their users to attract advertisers.

“When you use Google, you are making a deal. You get to use Gmail and search and YouTube and Google Maps for free and in exchange, you agree to share information about yourself. Google gets to sell that information to advertisers.

The more Google knows about you, the more it can match you to an advertiser who thinks you are an ideal customer. Advertisers are willing to pay more for ads served to ideal potential customers. For instance, airlines want to target people who love to travel. Children’s clothing makers want to target parents.

Google uses a lot of methods to learn about you. There’s the stuff you tell Google outright when you sign up for its services, like Gmail and Google Maps, or via an Android phone, like your name, phone number, location, and so on. Google also deduces information about you from watching your internet searches (what do you search for? click on?) and from the stuff you do with Google’s products.

By visiting a site called “Ads Settings” you can see what Google knows about you. It’s not that easy to find Ads Settings. First, click on the link below or type it into your browser: Then click on “Account history”.”

– “Here’s How To Figure Out Everything Google Knows About You” by Julie Bort on Business Insider