Chipotles are dried, smoked jalapeños; they have a sweet, smoky flavor.
Chipotle chile powder can substitue for whole chiles in some recipes as well as canned chipotle in adobo, rinsed of the adobo sauce.
The best dried chiles are the ones that have been sun-dried and not commercially oven-dried, which can make them bitter. Look for whole, not broken pods, with a uniform color. They should be be tough but still a little flexible.
Pull off or cut off the stems and dump out the seeds. Dried chiles can be crumbled or ground and added right to a dish. Or toast them lightly in a little hot oil to intensify their flavor. If puréeing dried chiles for sauce, rehydrate them first by soaking them (toasted or untoasted) in boiling water for a half hour or so.
Dried chiles will keep for months in a cool, dry place, though they may become more brittle over time.