NOV 18: Foreign Exchange Markets: A General Overview and Structure of the Forex Market
In the beginning countries would trade with each other using the barter system. If one nation needed lumber but had cattle, they would trade one product for another. This was pure trading.

The daily turnover on the FOREX market is somewhere around $1.2 trillion, so there is never any danger of an investor being unable to enter and exit positions whenever they want to. The fact is that the FOREX market never stops.