Most retail investors should spend time investigating a forex dealer to find out whether it is regulated in the U.S. or the U.K. (dealers in the U.S. and U.K. have more oversight) or in a country with lax rules and oversight. It is also a good idea to find out what kind of account protections are available in case of a market crisis, or if a dealer becomes insolvent.
An investor can profit from the difference between two interest rates in two different economies by buying the currency with the higher interest rate and shorting the currency with the lower interest rate. Prior to the 2008 financial crisis, it was very common to short the Japanese yen (JPY) and buy British pounds (GBP) because the interest rate differential was very large. This strategy is sometimes referred to as a "carry trade."
Loss aversion bias derives from the prospect theory. Humans have a funny way of evaluating their gains and losses, along with comparing their perceived meanings against each other. For example, when considering our options before making a choice, we are more willing to give preference to a lower possible loss over a higher possible reward. Fear is a much more powerful motivator than greed. In practice, a trader with a loss bias is more akin to cutting profits when they are still low, while allowing bigger drawdowns.
Imagine a trader who expects interest rates to rise in the U.S. compared to Australia while the exchange rate between the two currencies (AUD/USD) is 0.71 (it takes $0.71 USD to buy $1.00 AUD). The trader believes higher interest rates in the U.S. will increase demand for USD, and therefore the AUD/USD exchange rate will fall because it will require fewer, stronger USD to buy an AUD.
Since the market is made by each of the participating banks providing offers and bids for a particular currency, the market pricing mechanism is based on supply and demand. Because there are such large trade flows within the system, it is difficult for rogue traders to influence the price of a currency. This system helps create transparency in the market for investors with access to interbank dealing.