Hypothetically each trade provides for the other. You raise cattle, so you give the baker some butter, and milk, and the butcher some meat, and they give you back some bread and steaks. The carpenter builds your and their homes and you each give him some of your goods. It’s a great theory, and works well in small communes. Idk how it works in a global society, and considering all of the failures we’ve seen with it, I’m not sure if anyone else knows either. I’m aware this is like an elementary level explanation, and ignores a lot of concepts and examples, but I’m typing on a phone, and I’m sure someone else will expand upon it.