I am single and exempt why should I owe taxes?

Andrew_M asked:

My question is I am Single no dependents what so ever, I have no car, no mortgage, and received a full refund last year and expected to receive one again this year. I claimed exempt as I always have because like I said my refund status was good. I receive no government assistance what so ever. And lastly I barely make just over minimum wage. Why do I now owe money in taxes?
Oh and also why is that on the W4 form next to where you write Exempt does it say “This year I expect a refund of ALL federal income tax withheld because I expect to have NO tax liability.” If that’s not what it means?