A filter bubble is the intellectual isolation that can occur when websites make use of algorithms to selectively assume the information a user would want to see, and then give information to the user according to this assumption. Websites make these assumptions based on the information related to the user, such as former click behavior, browsing history, search history and location. For that reason, the websites are more likely to present only information that will abide by the user's past activity. A filter bubble, therefore, can cause users to get significantly less contact with contradicting viewpoints, causing the user to become intellectually isolated.

Personalized search results from Google and personalized news stream from Facebook are two perfect examples of this phenomenon.

Wikipedia