The spread, in Forex, is the difference between the bid and ask price of a currency pair. For example, if the Bid price of the EUR/USD is 1.16668, and the sell price is 1.16669, the spread will be 0.0001, or 1 pip. In any Forex trade, the value of a currency pair will need to cross the spread before it becomes profitable. To continue with the previous example, if a trader entered a long EUR/USD trade at 1.16668, the trade wouldn't become profitable until the value of the pair was higher than 1.16669.
One of the most unique features of the forex market is that it is comprised of a global network of financial centers that transact 24 hours a day, closing only on the weekends. As one major forex hub closes, another hub in a different part of the world remains open for business. This increases the liquidity available in currency markets, which adds to its appeal as the largest asset class available to investors.
The foreign exchange market is where currencies are traded. Currencies are important to most people around the world, whether they realize it or not, because currencies need to be exchanged in order to conduct foreign trade and business. If you are living in the U.S. and want to buy cheese from France, either you or the company that you buy the cheese from has to pay the French for the cheese in euros (EUR). This means that the U.S. importer would have to exchange the equivalent value of U.S. dollars (USD) into euros. The same goes for traveling. A French tourist in Egypt can't pay in euros to see the pyramids because it's not the locally accepted currency. As such, the tourist has to exchange the euros for the local currency, in this case the Egyptian pound, at the current exchange rate.