Questions on United States Economy?

Okay so in the U.S. how do people recieve and exchange goods (be specific)? Also the U.S. dollar is the currency in the U.S., how is it dispersed and exchanged among people? Finally, how is the value determined for belongings and currency in the U.S.? Thank you in advance for helping me. I'm interested to know the answers. Also if you have any good websites about the U.S. economy that would be very much appreciated.