Controversy about currency speculators and their effect on currency devaluations and national economies recurs regularly. Economists, such as Milton Friedman, have argued that speculators ultimately are a stabilizing influence on the market, and that stabilizing speculation performs the important function of providing a market for hedgers and transferring risk from those people who don't wish to bear it, to those who do.[79] Other economists, such as Joseph Stiglitz, consider this argument to be based more on politics and a free market philosophy than on economics.[80]

Just like stocks, you can trade currency based on what you think its value is (or where it's headed). But the big difference with forex is that you can trade up or down just as easily. If you think a currency will increase in value, you can buy it. If you think it will decrease, you can sell it. With a market this large, finding a buyer when you're selling and a seller when you're buying is much easier than in in other markets. Maybe you hear on the news that China is devaluing its currency to draw more foreign business into its country. If you think that trend will continue, you could make a forex trade by selling the Chinese currency against another currency, say, the US dollar. The more the Chinese currency devalues against the US dollar, the higher your profits. If the Chinese currency increases in value while you have your sell position open, then your losses increase and you want to get out of the trade.
Foreign exchange is traded in an over-the-counter market where brokers/dealers negotiate directly with one another, so there is no central exchange or clearing house. The biggest geographic trading center is the United Kingdom, primarily London. In April 2019, trading in the United Kingdom accounted for 43.1% of the total, making it by far the most important center for foreign exchange trading in the world. Owing to London's dominance in the market, a particular currency's quoted price is usually the London market price. For instance, when the International Monetary Fund calculates the value of its special drawing rights every day, they use the London market prices at noon that day. Trading in the United States accounted for 16.5%, Singapore and Hong Kong account for 7.6% and Japan accounted for 4.5%.[3]

For example – the rate you find for GBP/USD represents the number of US dollars one British pound will buy you. So, if you have reason to believe the pound will increase in value versus the US dollar, you’d look to purchase pounds with US dollars. However, if the exchange rate climbs, you’d sell your pounds back and make a profit. Likewise with Euros, Yen etc
Due to the ultimate ineffectiveness of the Bretton Woods Accord and the European Joint Float, the forex markets were forced to close[clarification needed] sometime during 1972 and March 1973.[43] The largest purchase of US dollars in the history of 1976[clarification needed] was when the West German government achieved an almost 3 billion dollar acquisition (a figure is given as 2.75 billion in total by The Statesman: Volume 18 1974). This event indicated the impossibility of balancing of exchange rates by the measures of control used at the time, and the monetary system and the foreign exchange markets in West Germany and other countries within Europe closed for two weeks (during February and, or, March 1973. Giersch, Paqué, & Schmieding state closed after purchase of "7.5 million Dmarks" Brawley states "... Exchange markets had to be closed. When they re-opened ... March 1 " that is a large purchase occurred after the close).[44][45][46][47]
How much each pip is worth is called the "pip value." For any pair where the USD is listed second, the above-mentioned pip values apply. If the USD is listed first, the pip value may be different. To find the pip value of the USD/CHF, for example, divide the normal pip value (mentioned above) by the current USD/CHF exchange rate. A micro lot is worth $0.10/0.9435 = $0.1060, where 0.9435 is the current price of the pair. For JPY pairs (USD/JPY), go through this same process, but then multiply by 100. For a more detailed explanation, see Calculating Pip Value in Different Forex Pairs.
In the futures market, futures contracts are bought and sold based upon a standard size and settlement date on public commodities markets, such as the Chicago Mercantile Exchange. In the U.S., the National Futures Association regulates the futures market. Futures contracts have specific details, including the number of units being traded, delivery and settlement dates, and minimum price increments that cannot be customized. The exchange acts as a counterpart to the trader, providing clearance and settlement.