Ancho Chile

Ancho chiles are the dried version of poblano peppers commonly used in Mexican and Southwestern U.S. cuisine.

The pepper is the dried version of the poblano pepper. To be specific, it is the dried version of the ripe version of the poblano pepper.

In other words, the chiles we know as poblano peppers are fresh chiles that are harvested before ripening, which is why they are green.

When allowed to ripen, poblanos turn red and develop additional sweetness, which in turn balances out their already mild heat. Thus, anchos are red while poblanos are green.

Incidentally, the word ancho translates to "wide" in English, while poblano refers to the state of Puebla in central Mexico where the peppers are supposed to originate.

So ancho chiles are what you get when you dry poblanos, and it is done for the purpose of preserving them.

Drying the chiles does not affect their heat, although the way the heat is transmitted will depend on how finely crumbled/ground they are, and whether they are reconstituted first or not. In other words, crumbled up chiles will give you a more localized spiciness whenever you happen to get a piece in a particular bite. Alternatively, you might get several. Whereas ones that are reconstituted first and then puréed will disperse their heat more evenly throughout.

Ancho chiles have a deep red color and a wrinkled skin. Sweet and smoky with a flavor slightly reminiscent of raisins, their heat is mild to medium-hot.

Ancho chiles register between 1,000 and 2,000 Scoville heat units, which means they are quite mild.

They are sometimes incorrectly referred to as pasilla peppers (as are poblanos, for that matter) but they are not the same thing.