As with all herbs and spices, buy them in small amounts, store them in glass jars in a dark, dry place, labeled with contents and date, and plan to replace them at least once a year. These are the heart and soul of Mexican cuisine. When fresh, chiles are considered a vegetable. In their dry whole, crushed or powdered form, they are considered a spice. This common ingredient adds heat and just a little chile flavor.
Chili powder is a mixture of ground chile, cumin, salt and garlic powder.
Sometimes it also includes cloves, allspice, coriander and powdered dried onion. There are several brands of commercially prepared chili powder. Recipes may call for whole cumin seed or for ground cumin. My preference is to buy the seed, and if a recipe calls for ground, I simply grind it myself. They have a spicy, slightly sweet orange flavor.