Mexican cuisine is known for its extensive flavor profile and use of local ingredients. This includes its dried chiles, which are used in many different ways to add flavor and spice to dishes.

Ancho chile can be used dried or rehydrated, whole or ground. It's usually incorporated before cooking sauces, blended with other spices or vegetables to make a base for a stew or soup, or sprinkled on top of meat, poultry, or seafood as part of a rub or marinade before cooking.
Chipotle peppers are smoked, dried jalapeño peppers, and as such they share the same medium-level heat as jalapeños (2,500 to 8,000 Scoville heat units.) It’s a popular chili pepper variety in both Mexico and North America and growing fast in favor across the globe because of its smoky, earthy flavor. 
Guajillo chilies are sometimes used to make a salsa for tamales; the dried fruits (chilies) are seeded, soaked, or simmered, then pulverized or mashed/pureed into a paste, then cooked with several other ingredients to produce a flavorful sauce.