The following came from a discussion I had with a student after I had defined central planning and markets. It is, of course, paraphrased:
Student: Aren't firm's basically centrally planned units?
Me: Yes. So is a household. But a firm typically doesn't oversee and plan an entire market. In fact, you can argue that I am centrally directed from here (motions to head). So markets are collections of centrally-planned units.