If I had to choose just one ingredient to take to a desert island, it would probably be this one. Extra virgin olive oil is the thread that runs through almost every recipe on this site: in soffritti, marinades, raw soups, and in place of butter to finish a risotto.
Extra virgin means it is obtained by mechanical means only, cold pressed, with very low acidity. The rest depends on the olive variety, the land and the time of harvest: some oils are fruity and gentle, others bitter and peppery, tickling your throat, a sign of olives picked while still green.
A tip: keep two bottles in the pantry, a simpler one for cooking and a bold one for the final raw drizzle, the one that makes all the difference on a bean soup or a bruschetta. And store it in the dark, away from the stove.