Simplest and most straightforward way of exchanging value between individuals.
Problems of Coincidence of Wants
Coincidence in scales
One party has a good that cannot be divided into small enough pieces to exchange for the value of what the other party has to offer
Coincidence in time frames
I have a bunch of apples but I want something that is durable and long-lasting. My apples may rot before I can make the trade.
Coincidence of locations
The thing I want to exchange for is too far away to transport what I can offer (maybe I am offering to trade a heavy rock)