Olive oil is an amazing thing. It is high in mono-unsaturated fats that are clinically proven to lower your LDL or "bad" cholesterol levels and loaded with anti-oxidants and flavonoids that help the body in defense against aging and disease. But it can be a little confusing when you are trying to select one to use in preparing meals.
Extra Virgin olive oil is from the first pressing of the olives and are certainly the finest of the olive oils, it also has a lower acidity than subsequent pressings and contains higher levels of phytochemicals that are beneficial to our health.
Virgin olive oils are from later pressings in which heat and chemical extraction methods are used, they are also more likely to be from mixed regions or other countries.
Light olive oil refers to the color and flavor of the oil -- not the amount of calories. It has a milder flavor and is more suited to everyday kitchen use rather than the darker, more heavily-flavored oils.
Try to select oils that are stored in tightly-sealed, dark-tinted containers as air and sunlight will spoil your precious oil. Remember, though, that all olive oils are high in fat, dense in calories and should be enjoyed in conservative amounts.