Extra-virgin olive oil comes from the first pressing of the olives. It contains no more than eight percent acidity (oleic acid), and has higher levels of Vitamin E, Vitamin A, chlorophyll, and magnesium. Whereas virgin olive oil is is made with olives that are slightly riper than those made with the extra-virgin oil. It has an acidity of less than two percent, and while it has a good flavor, extra-virgin's flavor is considered much more appetizing.
And when you see the term "refined" on a label, it means that the oil has been chemically treated to neutralize the strong acid taste. Know that if the label doesn't specify "extra-virgin" or "virgin," it more than likely contains refined oil — to be called extra-virgin or virgin, the olive oil cannot contain refined oil.