schrepfer.io
«Web tracking [or user tracking] means that users are tracked by third-parties while surfing the world wide web. These third-parties can see which web sites one opens. The tracking operates over multiple [seemingly independent] websites.»
source (translated): fraunhofer.de
(1) IP Tracking
University
WiFi
10.125.64.201
(2) Cookies
https://www.facebook.com/v2.8/
plugins/like.php?app_id=113869198 [...]
https://www.fancy-blog.com
Example: Facebook Like Button (Social Plugin)
online-shop.com
flight-search.ch
political-party.ch
news.ch
Example: Facebook Like Button (Social Plugin)
User Profiles
Collected data leads to user profiles. Such a profile may contain a user's hobbies, age, sex, pregnancy, eating habits, political interests, etc.
Constrained view of the Internet
Companies may only display contents they think you are going to like (algorithm-based). Prices of products may vary to maximize a company's benefits (e.g. airplane websites)
No use of cookies
Leads to loss of user convenience in web browsing
Incognito Mode
Removes browser data every time the browser window is closed
Tools to prevent tracking
AdBlock and Ghostery can prevent tracking