Olives picked straight off the tree taste disgusting, so they are soaked in oil, water, brine or even a strong alkaline solution to remove bitter chemicals.
The oil from the fruit has a long history of use in lamps and anointing the brave; now it is used mostly in the kitchen and is thought to reduce cholesterol levels and deter heart disease. There is as much variation in taste and character in olive oil as there is in wine. The oil is also still used for massage and in cosmetics and soaps.
Spain is the largest producer of olives, then Italy and Greece. The average Greek consumes 22 litres of olive oil a year; in the UK we use under half a litre.