There are many varieties of olives, and they vary tremendously in size and flavour. Fresh olives are incredibly bitter and the final flavour depends on how ripe the olive is when picked, and the processing it receives. Under ripe olives are green, whereas ripe olives may be either green or black. The olive is naturally bitter as the raw olive contains an alkaloid that makes them bitter and unpalatable and requires a multi-step curing process to become edible, firstly soaked in a lye solution, then fermented in brine or salt to reduce bitterness and tenderise the flesh.

Olives that are picked when they are riper contain more oil and are deeper in colour. The common black olive is a ripe green olive that gets its characteristic colour and flavour from lye curing and oxygenation. Olives that are tree ripened turn dark brown or black naturally. Most of these olives are used for oil, the rest are brine or salt cured and are usually packed in olive oil or vinegar solution. Kalamata is one of the most popular of the imported ripe olives. Dry cured olives have been packed in salt, which removes most of their moisture and creates dry, wrinkled fruit with an intense flavour.