The chilacas, similar to the American Anaheim, are long, thin chiles, that sometimes twist and have a shinny light green color. Their heat goes from mild to mildly hot, but they are never very spicy.
Chilacas are very meaty and are used many times as a vegetable. Most times charred, peeled, and seeded, like the Poblanos, they are used for side dishes like rajas sauteed with onions and sometimes cream and cheese. I ate this version many times in the state of Chihuahua, in the North of Mexico. They are also used for eggs, sauces, soups, casseroles and fillings, amongst other things.
Chilacas become Pasillas when dried, and turn raisin black in color and interestingly bitter in flavor. They are sometimes confused with the New Mexico chile when dried, as they are and look similar, but the later is hotter.