Commerce Planets are, essentially, large bazaars that take up the entirety of a planet. These planets are often rather small and, though inhabited, may not have any indigenous civilizations living on them. Commerce planets are not especially common, although two of them can be found in the Uncharted Territories. The first planet visted by John Crichton after arriving in that region of the Delta Quadrant was, in fact, a commerce planet.
Commerce planets appear in the first season of Farscape.