Many different types of dried chili peppers exist, and essentially any type of fresh chili can be dried to make one. The most common types of dried chili peppers include the ancho, guajillo, mulato, and chilpotle peppers. Other types include the cascabel, the de arbol, the pasilla, and the seco del norte. Several other chilis, including the bhut jolokia and the scotch bonnet can also be dried, but they are also commonly used fresh. Most dried chili peppers are simply left out in the sun for a couple of days to dry them out.
In Mexico, the ancho is the most common of the dried chili peppers. The word ancho literally means "wide," which is the chilis defining characteristic. Ancho chilis are also red to brown in color and have wrinkled skin. As the chili dries, the skin becomes darker and darker, and it is often necessary to cut it open to distinguish it from the mulato, another common type of dried chili. The ancho chili is generally used in sauces after being re-hydrated.
The guajillo is another one of the most common dried chili peppers. This chili is long and thin, with a characteristic point at the end. The skin is dark red in color, with hints of purple in certain places, and doesn’t wrinkle in the way the ancho does. Guajillo skin can be quite tough, and as a result many people choose to remove it before cooking with it. As a common and relatively cheap chili, it is also generally used in sauces.
Chilpotles are dried chili peppers actually made from dried jalapeño peppers. The fresh pepper is dried and cured with smoke to make the chilpotle. Ordinarily, the skin is light brown in color with a faint golden tint, and tough to the point of leatheriness. The chili has a slightly fruity flavor, and is very spicy — between 2,500 and 8,000 units on the Scoville chart. Scovilles are the accepted unit of measurement for spiciness.
Virtually any type of fresh chili can be dried and turned into a variety of dried chili peppers. The hottest naturally-occurring chili pepper is the bhut jolokia, commonly called the ghost chili. This measures at 1,001,034 Scovilles, and the dried version of it is just as spicy. Chilis can be dried by leaving them out in the sun for a few days, putting them in the oven or hanging them up.