Chorizo varies according to its country of origin and, within that, the region where it's produced. It is mostly found in places once colonised by Spain or Portugal.
What is it? Most chorizo is made from pork but there are exceptions, such as those made from beef. The Mexican variety is fresh, uncured, spicy, soft and fatty. It's sold loose or stuffed into inedible plastic casings, out of which the meat is squeezed before cooking.
Portuguese chourico is easy to find in Macau and the Spanish style is readily found in Hong Kong. These pork sausages tend to be firm and are flavoured with paprika and other spices then stuffed into edible casings. They are cured either by smoking or drying in environment-controlled rooms.
What to look for: some chorizo is hot, other types are sweet, and it can be lean or fatty, firm or soft.
How is it available? In links, usually in the refrigerated section of the supermarket. However, in Spain and Portugal chorizo is not always kept cold since it is, by definition, a preserved meat. Chorizo can also be immersed in fat then canned.
What else: Mexican chorizo is difficult to find in Hong Kong, but it's not difficult to make because it doesn't need to be stuffed into casings. The Portuguese and Spanish varieties usually don't require cooking but the Mexican type does.