What do "virgin" and "extra virgin" mean in regards to olive oil?
In the US, "extra virgin" isn't a legally protected term - some of the stuff sold as EVOO here would never, ever pass as it elsewhere.

From Wikipedia:


Extra-virgin olive oil comes from virgin oil production only, contains no more than 0.8% acidity, and is judged to have a superior taste. Extra Virgin olive oil accounts for less than 10% of oil in many producing countries. It is used on salads, added at the table to soups and stews and for dipping.
Virgin olive oil comes from virgin oil production only, has an acidity less than 2%, and is judged to have a good taste.
Pure olive oil. Oils labeled as Pure olive oil or Olive oil are usually a blend of refined and virgin production oil.


Cooking-wise, the extra virgin stuff is best used in situations where it won't be highly heated. Salad dressings, dipping oils, finishing a dish, etc. are where it shines.