Olive oil goes back thousands of years but recently is making headlines for it healthy properties including its antioxidant properties. For the rest of us, it is a wonderful ingredient to cook with or use as is.
Olive oil comes with many names like Virgin, Extra Virgin, Pure, Lite and what they discribe are how the oil is processed. Olives come from olive trees and are pressed to create olive oil. How they are pressed, the extraction method and how they are handled afterward is how one determines what label they receive.
Virgin Olive Oil is mechanicall extracted by machines but with no chemicals.
Extra Virgin Olive Oil is also mechanically extracted but must be judged both analytically as well as taste tests to determine that the oil is free from defects. Any oil found with slight defects but can be consumed by humans is rated, FINE.
Pure olive oil and light olive oil are blends of cheap "Refined" oil with virgin oil. The ratio is typically 95% refined oil or pomace with just 5% virign oil. They are cheap to produce but you may not find those saving at the grocery store. For what's in them, they are not a bargin. You might as well call them "impure".
The bottom line is you want to buy "extra virgin" olive oil for the biggest bang for your buck. It is an all natural product with distinctive flavors based on where it comes from and should taste clean and not overpowering.
Spain produces the largest amount and some of the finest olive oil in the world.
Much of what is sold as "Italian Olive Oil" is really oil imported from Spain, packaged in Italy and sold as Italian.
Extra Virgin Olive may have sediment at the bottom of the bottle.
Just because olive oil is marked "Extra Virgin" doesn't mean it is. If the cost of the oil looks to inexpensive for the real thing, it most likely is.
Olive oil should not be refrigerated but should be stored in a cool dark space.
Olive oil should be stored for up to a year. Heat and light can really shorten its shelf life.
Olive oil does not get better with age. Use it or loose it.
Extra Virgin Olive because of its low acidity has the lowest chance of going rancid.
There is nothing wrong with using olive oil for frying because it is the slowest oil to decompose.