Once Nixon abolished the gold standard, the dollar's value quickly plummeted. The dollar index was established to give companies the ability to hedge this risk. Someone created the U.S. Dollar Index to give them a tradeable platform. Soon, banks, hedge funds, and some speculative traders entered the market. They were more interested in chasing profit than in hedging risks. 
At the end of 1913, nearly half of the world's foreign exchange was conducted using the pound sterling.[24] The number of foreign banks operating within the boundaries of London increased from 3 in 1860, to 71 in 1913. In 1902, there were just two London foreign exchange brokers.[25] At the start of the 20th century, trades in currencies was most active in Paris, New York City and Berlin; Britain remained largely uninvolved until 1914. Between 1919 and 1922, the number of foreign exchange brokers in London increased to 17; and in 1924, there were 40 firms operating for the purposes of exchange.[26]

On 1 January 1981, as part of changes beginning during 1978, the People's Bank of China allowed certain domestic "enterprises" to participate in foreign exchange trading.[51][52] Sometime during 1981, the South Korean government ended Forex controls and allowed free trade to occur for the first time. During 1988, the country's government accepted the IMF quota for international trade.[53]

International parity conditions: Relative purchasing power parity, interest rate parity, Domestic Fisher effect, International Fisher effect. Though to some extent the above theories provide logical explanation for the fluctuations in exchange rates, yet these theories falter as they are based on challengeable assumptions [e.g., free flow of goods, services and capital] which seldom hold true in the real world.
A trader thinks that the European Central Bank (ECB) will be easing its monetary policy in the coming months as the Eurozone’s economy slows. As a result, the trader bets that the euro will fall against the U.S. dollar and sells short €100,000 at an exchange rate of 1.15. Over the next several weeks the ECB signals that it may indeed ease its monetary policy. That causes the exchange rate for the euro to fall to 1.10 versus the dollar. It creates a profit for the trader of $5,000.
To use Gold CFD as an example, at the time of writing, to purchase an ounce of Gold you would need to spend 1,200 USD. However, with a leverage rate of up to 1:20 (which means a trader could trade up to 20 times the value of what they deposit), a trader could trade on the full value of an ounce of gold (equivalent to 1,200 USD), for a deposit of just 60 USD.
Hedge funds – Somewhere around 70 to 90% of all foreign exchange transactions are speculative in nature. This means, the person or institutions that bought or sold the currency has no plan of actually taking delivery of the currency; instead, the transaction was executed with sole intention of speculating on the price movement of that particular currency. Retail speculators (you and I) are small cheese compared to the big hedge funds that control and speculate with billions of dollars of equity each day in the currency markets.
Use a stop loss: A stop loss is tool that traders use to limit their potential losses. Simply put, it is the price level at which you will close a trade that isn't moving in your favour, thereby preventing any further losses as the market continues to move in that direction. You can also use a stop loss to conserve any profits you might have already made - the tool to achieve this is known as a 'trailing' stop loss, which follows the direction of the market.
There are two main types of retail FX brokers offering the opportunity for speculative currency trading: brokers and dealers or market makers. Brokers serve as an agent of the customer in the broader FX market, by seeking the best price in the market for a retail order and dealing on behalf of the retail customer. They charge a commission or "mark-up" in addition to the price obtained in the market. Dealers or market makers, by contrast, typically act as principals in the transaction versus the retail customer, and quote a price they are willing to deal at.
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.