Extra virgin and virgin olive oil, like fresh fruit juice, are simply made by crushing olives. Extra virgin tastes better than virgin, hits higher scores in terms of its chemical composition and it has more nutrients.
All other grades, including “olive oil,” “pure" and "light" olive oil are refined, which means they are made in an industrial process using heat and chemicals -- the same process used to make seed oils like canola and sunflower. Refined olive oil, a monounsaturated fat, is still a much healthier choice than seed oils.
Source: Olive Oil Times