A swap trade involves both. Dealers buy a currency at today's price on the spot market and sell the same amount in the forward market. This way, they have just limited their risk in the future. No matter how much the currency falls, they will not lose more than the forward price. Meanwhile, they can invest the currency they bought on the spot market.
For instance, if you opened a long trade on the GBP/USD currency pair, and the pair increased in value, the price limit at which the trade should close (the stop loss) would climb alongside the price of the currency pair. If the value of the GBP/USD then started to fall, the trade would be closed as soon as it hit your stop loss, preserving any profits you had made beforehand.
None of the models developed so far succeed to explain exchange rates and volatility in the longer time frames. For shorter time frames (less than a few days), algorithms can be devised to predict prices. It is understood from the above models that many macroeconomic factors affect the exchange rates and in the end currency prices are a result of dual forces of supply and demand. The world's currency markets can be viewed as a huge melting pot: in a large and ever-changing mix of current events, supply and demand factors are constantly shifting, and the price of one currency in relation to another shifts accordingly. No other market encompasses (and distills) as much of what is going on in the world at any given time as foreign exchange.
With the expansion of retail brokers (which, of course, should always be regulated), the population size of intraday traders operating in a specific intraday time frame (M1-H1) determines the profitability of the trader trading this time frame. As the number of traders trading certain intraday time frames increases, conversely, the competition also increases, and the markets may become more efficient and easier to trade.
Unlike stock markets, which can trace their roots back centuries, the forex market as we understand it today is a truly new market. Of course, in its most basic sense - that of people converting one currency to another for financial advantage - forex has been around since nations began minting currencies. But the modern forex markets are a modern invention. After the accord at Bretton Woods in 1971, more major currencies were allowed to float freely against one another. The values of individual currencies vary, which has given rise to the need for foreign exchange services and trading.