No where in global cuisine is the chili celebrated more than it is in Mexico. There is literally hundreds of varieties, some are used fresh and other dried - the chipotle is a smoked jalapeno chili.
Chipotles in Adobo are essentially dried chipotle chilies re-hydrated in Adobo sauce which is a sweet and tangy puree of tomatoes, garlic and vinegar. They are awesome chopped into salsas and stews and are an essential ingredient for Tinga Chicken, a classic taco filling. This jar is really handy for keeping them in your fridge once opened.