One pound on Monday can bring you 1.19 euros. On Tuesday 1.20 euros. This tiny change may not seem like a big deal. But think about it on a larger scale. A large international company may have to pay foreign employees. Imagine what this can do for a practical purpose, if, as in the example above, a simple exchange of one currency for another costs you more, depending on when you do it? These few kopecks add up quickly. In both cases, you, as a traveler or business owner, can keep your money until the forex course becomes more favorable.
Currency trading was very difficult for individual investors prior to the internet. Most currency traders were large multinational corporations, hedge funds or high-net-worth individuals because forex trading required a lot of capital. With help from the internet, a retail market aimed at individual traders has emerged, providing easy access to the foreign exchange markets, either through the banks themselves or brokers making a secondary market. Most online brokers or dealers offer very high leverage to individual traders who can control a large trade with a small account balance.
There are scheduled news releases that come out daily, and certain news releases like Non Farm Payrolls and rate decisions have a massive affect on the markets. It is important to know when these news releases are due, and before the start of each month you should make a note of the important ones. I have a up-to-date economic calendar on this site which you can access here.
More specifically, the spot market is where currencies are bought and sold according to the current price. That price, determined by supply and demand, is a reflection of many things, including current interest rates, economic performance, sentiment towards ongoing political situations (both locally and internationally), as well as the perception of the future performance of one currency against another. When a deal is finalized, this is known as a "spot deal." It is a bilateral transaction by which one party delivers an agreed-upon currency amount to the counter party and receives a specified amount of another currency at the agreed-upon exchange rate value. After a position is closed, the settlement is in cash. Although the spot market is commonly known as one that deals with transactions in the present (rather than the future), these trades actually take two days for settlement.