Forex trading does take place daily, where almost two trillion dollars are moved every day - that is a huge amount of money. Think about how many millions it does take to bring about a total of a trillion and then consider that this is done on a daily basis - if you want to get involved in where the money is, forex trading is one 'setting' where money is exchanging hands daily.
The currencies that are traded on the forex markets are going to be those from every country around the world. Every currency has it own three-letter symbol that will represent that country and the currency that is being traded. For example, the Japanese yen is the JPY and the United Stated dollar is USD. The British pound is the GBP and the Euro is the EUR. You can trade within many currencies in one day, or you can trade to a different currency every day. Most all trades through a broker, or those any company are going to require some type of fee so you want to be sure about the trade you are making before making too many trades which are going to involve many fees.