The filter bubble is the idea that internet companies are constantly tailoring content for you based upon your past internet interactions. Companies track what you click, what you search for, what you like, where you are searching, and how long you stay on a page. Those ideas are used to create a profile of you. They then customize your internet experience to those preferences; ads and social media links are tied to your past.
The outcome of this is that the internet (actually your browser and social media accounts) is actively limiting your availability to see all that is on the internet; it filters out things that are not like what you have viewed in the past. This creates a bubble or an isolation; you will only see what you have seen before (or very similar). In the long term you will then only see things that you like. That even applies to news coverage, opinions, and search results. Facebook, Twitter, and Google all work on creating this filter. For the companies it is about money. The more posts/ads/tweets that you "like" or click on the more money the company makes. Your profile, search history, internet habits are being sold to advertisers without your knowledge.
This is bad, in the long term. It means that you are constantly being fed news feeds, opinions, and advertisements that are things you already like. It eliminates/filters out things that you might disagree with. In the end, you are rarely shown opposing ideas, or become aware that millions of others may disagree with you. The presidential election of 2016 is one big example of people being unaware of what others think and feel. Millions thought that Hillary Clinton would walk away with the election, but she lost. Many, especially political commentators, were shocked when Donald Trump won. They were shocked because everything they read was already in agreement with their opinion. The opinions of millions were left out of their search results and feeds. Liberal America and the mainstream media were blindsided by an incredibly large minority that voted for Trump.
Eli Pariser later created a list of 10 things to do to burst the bubble.
1 - get rid of cookies - cookies are created by companies when you visit their websites (or even if you just see an ad) and are a small file that is stored on your computer. Within most browsers, it is a "history" or "privacy" setting.
2 - Erase your web history - your browser stores your history of searches and of website visits. By clearing your history you erase your tracks of where you have been. This then eliminates your past and makes it more difficult to construct your profile.
3 - Tell all your social media favorites to keep data private (or don't post it at all) - change you settings to as private as you feel comfortable. Don't post anything you don't want the entire world accessing.
4 - Remove your real birthday from social media - posting your true birthday makes it easy to match your various profiles together. This then lets companies merge profiles and have an even better picture of who you are.
5 - Turn off targeted ads - change your settings to not allow targeted ads. Now you shouldn't see the same ad from site to site.
6 - Go incognito - turn on "incognito" or "private browsing" in your browser. These settings turn off browsing history and block cookies. They may also sign you out of Google, Facebook, and others.
7 - Go anonymous - use a VPN or install a privacy browser. A privacy browser basically disables things similar to "incognito" mode. A VPN sends all internet traffic through another server in another location; it hides you from some of the internet's tracking services. Go dark by using TOR as a browser.
8 - Depersonalize your browser - within your browser settings, keep it from sending information out (as much as possible).
9 - Tell Google and others to make it easier to see and control your filters - write to the various companies and complain.
10 - Tell Congress you care - write a letter asking them to pressure companies to make filters easier to see and set.
One additional comment from the librarian - search using a search engine that doesn't save searches