Form
There are 2-types of garlic, Softneck and Hardneck. 
The Softneck variety is the commonly cultivated form and is normally available at vegetable shops. The leaves are basal with no central stalk and rarely produce flowers or aerial bulbs. 

It produces large bulbs with many cloves that are arranged in layers and are surrounded by a thin papery tunic. There are 2-further subgroups, the silverskin which store well and have a smooth silvery white tunic and the artichoke types that have obvious overlapping cloves.

The Hardneck variety may also be known as Serpent garlic and forms a woody base and producers a curved or coiled flowers scape (stem) in bud with a terminal cluster of flowers or producers bulbils. 

The dark green linear leaves are entire and the small bulbs are reduce a single layer of uniform cloves that are arranged around a central stem. 

There are 3-further subgroups, the rocambole which produces large cloves with a tan coloured tunic, the Porcelain type that produces only a few but large cloves and Purple stripe that produces several cloves that are enclosed in a colourful tunic. The hardneck varieties require a cold winter for best bulb production and grow best in cold temperate regions.