This pasta dish is characterized by the inclusion of a fresh chili pepper in a simple sauce of tomatoes cooked in garlic-scented oil. Arrabbiata is an Italian word for angry; that's the chili pepper. Naturally depending upon your tolerance for angry tomatoes, you can add as much chili pepper as you like. This version is quite mild, with just the taste of the pepper and very little heat.
You can use dry or fresh chilies. If you use dried chilies, don't chop them and then they are easy to remove so nobody accidentally get more than they expected.
This is traditionally served with short pasta like penne or ziti.