When you are "buying" or "selling", you generally are using money, or cash. This cash actually doesn't have ANY value on its own. The value is only given to these paper money based on the amount the government & the WTO sets. For example, the US used to have a high amount (per trade as compared to other world currencies), as it was bound by the gold standard, in which the US would only print so much per oz of gold. However, the demand for more money as well as the leak of gold to other countries led to the US not using the gold standard anymore.
In the end, just remember that any kind of buying & selling (must go together), bartering of goods (trading), are all forms of trades.
In trade, barter (derived from baretor) is a system of exchange where participants in a transaction directly exchange goods or services for other goods or services without using a medium of exchange, such as money.
