It goes by various names; a longtail or a Sport Utility Bicycle (SUB). More specifically it's a Marin Novato with an Xtracycle Freeradical conversion kit. And even more specifically, mine is named Lakshmi, after the Hindu goddess of good fortune.
The Xtracycle combination means you'll rarely have the excuse of saying, "But I can't carry..."
Here's an example of a typical load: 80" bi-fold door and other miscellaneous stuff from Lowes, plus four bags of groceries from the produce stand and the supermarket; all in one 10-mile round trip.
For more examples of what people carry on SUBs, go here.