Native to central America, there are four main varieties: Hass (considered to be the best), which has a dark, knobbly skin; the pear-shaped, smooth-skinned Ettinger and Fuerte (of which a tiny, baby-sized variety is also available); and the more spherical Nabal.
Highly nutritious, containing vitamin E, iron, potassium and niacin, it's also unique among fruits in that it contains oil - but most of it is the good, monosaturated type.
Once ripe, keep them in the fridge.
Native to central America