When you trade forex, you're effectively borrowing the first currency in the pair to buy or sell the second currency. With a US$5-trillion-a-day market, the liquidity is so deep that liquidity providers—the big banks, basically—allow you to trade with leverage. To trade with leverage, you simply set aside the required margin for your trade size. If you're trading 200:1 leverage, for example, you can trade £2,000 in the market while only setting aside £10 in margin in your trading account. For 50:1 leverage, the same trade size would still only require about £40 in margin. This gives you much more exposure, while keeping your capital investment down.

The possibility of losing your investment is high, so it is advisable to only use risk capital (money that you can afford to lose) when engaging in Forex trading. The Forex market offers high levels of leverage to traders. Leverage has both the possibility of high returns and high losses, and should only be used with discretion. Be disciplined and don't be tempted to overtrade.
The practice of taking on excessive risk does not equal excessive returns. Almost all traders who risk large amounts of capital on single trades will eventually lose in the long run. A common rule is that a trader should risk (in terms of the difference between entry and stop price) no more than 1% of capital on any single trade. Professional traders will often risk far less than 1% of capital.

Forex trading scams are a concern for even the savviest investor. Foreign exchange fraud has been on the rise for the last few decades, leading the Commodities Futures Trading Commission and other agencies to deploy task forces analyzing and curtailing schemes. The ingenuity of fraudulent schemes, whether they’re based on phony software or creating fake accounts, increases, but their telltale signs remain largely the same. Steer clear of forex brokerages promising sure wins, fast results, or secret formulas for success. The market has proved time and again that there are no shortcuts. Scammers bank on the human propensity to believe otherwise.
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
Asset market model: views currencies as an important asset class for constructing investment portfolios. Asset prices are influenced mostly by people's willingness to hold the existing quantities of assets, which in turn depends on their expectations on the future worth of these assets. The asset market model of exchange rate determination states that “the exchange rate between two currencies represents the price that just balances the relative supplies of, and demand for, assets denominated in those currencies.”
The foreign exchange market is unique for several reasons, mainly because of its size. Trading volume in the forex market is generally very large. As an example, trading in foreign exchange markets averaged $5.1 trillion per day in April 2016, according to the Bank for International Settlements, which is owned by 60 central banks and is used to work in monetary and financial responsibility. 
This information can then allow traders to make judgements regarding a currency pair's price movement. For example, if a Japanese candlestick closes near the highest price for the period, that would imply that there is a strong interest on the part of buyers for this currency pair during that time period. A trader might then decide to open a long trade to take advantage of that interest.

Currencies are traded against one another in pairs. Each currency pair thus constitutes an individual trading product and is traditionally noted XXXYYY or XXX/YYY, where XXX and YYY are the ISO 4217 international three-letter code of the currencies involved. The first currency (XXX) is the base currency that is quoted relative to the second currency (YYY), called the counter currency (or quote currency). For instance, the quotation EURUSD (EUR/USD) 1.5465 is the price of the Euro expressed in US dollars, meaning 1 euro = 1.5465 dollars. The market convention is to quote most exchange rates against the USD with the US dollar as the base currency (e.g. USDJPY, USDCAD, USDCHF). The exceptions are the British pound (GBP), Australian dollar (AUD), the New Zealand dollar (NZD) and the euro (EUR) where the USD is the counter currency (e.g. GBPUSD, AUDUSD, NZDUSD, EURUSD).
In the forex market currencies trade in lots, called micro, mini, and standard lots. A micro lot is 1000 worth of a given currency, a mini lot is 10,000, and a standard lot is 100,000. This is different than when you go to a bank and want $450 exchanged for your trip. When trading in the electronic forex market, trades take place in set blocks of currency, but you can trade as many blocks as you like. For example, you can trade seven micro lots (7,000) or three mini lots (30,000) or 75 standard lots (750,000), for example.
There are actually three ways that institutions, corporations and individuals trade forex: the spot market, the forwards market and the futures market. The forex trading in the spot market always has been the largest market because it is the "underlying" real asset that the forwards and futures markets are based on. In the past, the futures market was the most popular venue for traders because it was available to individual investors for a longer period of time. However, with the advent of electronic trading and numerous forex brokers, the spot market has witnessed a huge surge in activity and now surpasses the futures market as the preferred trading market for individual investors and speculators. When people refer to the forex market, they usually are referring to the spot market. The forwards and futures markets tend to be more popular with companies that need to hedge their foreign exchange risks out to a specific date in the future.