What is Harissa?

I bought a powdered blend from Kalustyans which has instructions on how to make it a paste. I simply LOVE it!

If you buy DEA harissa, be sure to refrigerate it. I didn't and it fermented in the tube, popped the seam and leaked. A lesson in "read the label..."

The first time I bought harissa, it came in a tube labelled "DEA" and among the ingredients were carrots and turnips, along with the chiles and spices you have all mentioned. Other brands that I've seen since don't seem to include the vegetables, so I'm wondering if anyone can clarify the difference.

Here's one recipe from the site, and you can find others here too.
http://www.food52.com/recipes/6388_harissa

Just to add to what the previous answers have correctly noted, more specifically it's typical of Tunisian and Morrocan cooking (usually as condiment, to say, a tagine). It also appears in Spain and France both of which have significant populations of North African immigrants. Other ingredients to harissa might include caraway and cardamom. It's good stuff if you can find it.

A chili sauce comprising chili peppers, spices, and oil that is used commonly in North African cooking. Harissa typically is quite spicy-hot and flavorful. It can be purchased in cans or jars in many supermarkets and specialty food stores, or you can make your own at home.

A spicy seasoning paste for african dishes. Usually quite fiery for american tastes!