Bias is when you take one persons side over the other. I took Trayvon's side because I knew his side, and I knew his parents side. I didn't know both sides. Or the truth. I was biased when I wrote this article.
It is easier to be biased than to tell the truth. Mostly because you do not always know the truth. There are three sides to every story (his side, her side, and the truth) and when you only know one side it is hard not to be biased.