Confirmation bias is the tendancy of people to favor information that confirms their own beliefs. An example would be my belief in animal rights tend to cause me to search for and gather information from sources that promote animal rights such as the SPCA or The Humane Society. I would stay away from other sources that may tell a more complete picture but are automatically discounted because they don't mesh with my beliefs.

Think about it for a second and I guarantee that you have similar biased beliefs. We all do. It's human nature and the best way to avoid making poor decisions based on a confirmation bias is to be aware of the way you think. The concept of "thinking about thinking" and questioning assumptions falls under the idea of critical thinking.

A couple years ago a journalist, David McRaney, wrote an article on his blog about confirmation bias. I highly recommmend taking the time to read and digest what he says...I am still processing it!