Anaheim - Also known as chile verde or simply green chiles, generally mild to medium hot with a slightly sharp, astringent taste. Best all-purpose chile
Ancho - Also known as Poblano or pasilla. Generally a touch hotter and richer in flavor than the Anaheim
Arbol - A long, pointed red chile 2 to 3 inches long; the stems are long and fine. A distinctive flavor with searing heat. Related to the cayenne, arbol is primarily used ground in sauces and you may see it referred to in soup and stew recipes.
Chipotle - These are smoke-dried jalapenos
Hatch - Also called New Mexican chiles, an anaheim chile grown ONLY in the Hatch area of New Mexico. These are only available certain times of the year and are much hotter than the regular anaheim.
Jalapeno - Green or red, hot to ultra hot with a distinctive flavor; use judiciously when flavoring and spicing dishes with this pepper
Pasilla and Poblano - see Ancho
Pequin - A tiny, round red chile. Adds incendiary punch when sparingly added to a recipe
Serrano - Green or red, these are very hot; also known as scotch bonnets
Yellow - also known as Banana peppers or Hungarian wax, sweet to medium hot.