Virgin olive oil has a higher acid level than is permitted in extra virgin (up to 2% free acid as opposed to maximum 0.8%). It may also have minor flaws in texture or flavour, not allowed in extra virgin oil. I can't remember ever having seen "virgin olive oil" in any shop. Only extra virgin ever crosses my threshold!

As far as I know, olive oil is the only kind of oil that is subject to these kinds of official standards. Even so, there is a lot of fake extra virgin stuff around. If it's in a plastic bottle or in clear glass, it's fake!