Virgin refers to "first". Virgin oil usually refers to the first batch of oil that is extracted after the first cold press. It is generally a little thicker and more stable under hotter conditions (cooking). "Extra virgin" refers to the very first cold press of the olives. This is the oil in its most raw and pure form. It is best consumed at room temperature, though is fine for light cooking. Refrigeration is always recommended for any oil.
Answer 2: Only extra virgin olive oil and virgin olive oil are direct extractions from the fruit. Refi ed or common olive oil and olive pomace are chemically treated to neutralize strong flavors. The oil's qualities last up to about 18 months. Light deteriorates it's components, so oil should be stoted in a cool, dark place.