3 Answers

Chorizo
There are two very different types of chorizo sausage. Though both are dark-red, spicy, garlicky, and made with pork, one is fresh, like Italian sausage, and the other is dry, like salami or pepperoni.

Mexican chorizo is made with fresh ground pork and seasoned predominantly with chiles. It is sold in the fresh sausage section of the supermarket, with bratwurst and breakfast links. It is usually squeezed from its casing into a skillet and pan-fried to the consistency of ground beef. If you can't find Mexican chorizo, spicy Italian sausage is a suitable substitute, although it will add a strong fennel flavor.

Spanish chorizo is made with cured or semi-cured chopped pork (usually smoked) and seasoned predominantly with smoky Spanish paprika. In Spain, every region has its own style of chorizo (called chouriço in Portugal)—softer or drier, spicier or sweeter, long and thin or short and fat. In the United States, it is generally a thin sausage that has been air-dried to a hard consistency. It is sold in the cured meats section of specialty foods stores and some supermarkets. It can be sliced for a sandwich or chopped and added to a dish. The closest substitute for Spanish chorizo is probably Portuguese linguiça, also a smoked, cured hard sausage.

Because chorizo comes in both fresh and dry forms, it's important to check the recipe to make sure which type of chorizo is called for.

Read More http://www.bonappetit.com/tipstools/ingredients/2009/07/chorizo#ixzz2JDStd8o3

Check here, Spanish is best IMO  >http://en.wikipedia.org/wiki/Chorizo

I've read many a package to be sure before I bought any. Most packs contained the glands of the animal. See here:  http://chowhound.chow.com/topics/340224