A) Currency :- In economics, currency refers to a generally accepted medium of exchange.

These are usually the coins and banknotes of a particular government, which comprise the physical aspects of a nation's currency (money) supply. The other part of a nation's money supply consists of bank deposits (sometimes called deposit money), ownership of which can be transferred by means of cheques, debit cards, or other forms of money transfer. Deposit money and currency are money in the sense that both are acceptable as a means of payment.

Money in the form of currency has predominated in human civilizations from about 10,000 BCE on. Usually (gold or silver) coins of intrinsic value (commodity money) have been the norm. However, nearly all contemporary money systems are based on fiat money – modern currency has value only by government order (fiat). Usually, the government declares the fiat currency (typically notes and coins issued by the central bank) to be legal tender, making it unlawful to not accept the fiat currency as a means of repayment for all debts, public and private.

B) Currency rate :- In finance, an exchange rate also known as the foreign-exchange rate, forex rate or FX rate between two currencies is the rate at which one currency will be exchanged for another.

It is also regarded as the value of one country’s currency in terms of another currency. Example, an interbank exchange rate of 91 Japanese yen (JPY, ¥) to the United States dollar (US$) means that ¥91 will be exchanged for each US$1 or that US$1 will be exchanged for each ¥91. Exchange rates are determined in the foreign exchange market,which is open to a wide range of different types of buyers and sellers where currency trading is continuous: 24 hours a day except weekends, i.e. trading from 20:15 GMT on Sunday until 22:00 GMT Friday. The spot exchange rate refers to the current exchange rate. The forward exchange rate refers to an exchange rate that is quoted and traded today but for delivery and payment on a specific future date.

C) Forex broker :- A forex broker is an individual or party (forex brokerage firm) that arranges transactions between a buyer and a seller, and gets a commission when the deal is executed. A forex broker who also acts as a seller or as a buyer becomes a principal party to the deal.

Individual Retail speculative traders constitute a growing segment of this market with the advent of retail foreign exchange platforms, both in size and importance. Currently, they participate indirectly through forex brokers or banks. Retail forex brokers, while largely controlled and regulated in the USA by the Commodity Futures Trading Commission and National Futures Association have in the past been subjected to periodic Foreign exchange fraud.[11][12] To deal with the issue, the NFA and CFTC began (as of 2009) imposing stricter requirements, particularly in relation to the amount of Net Capitalization required of its members. As a result many of the smaller and perhaps questionable forex brokers are now gone or have moved to countries outside the US. A number of the foreign exchange forex brokers operate from the UK under Financial Services Authority regulations where foreign exchange trading using margin is part of the wider over-the-counter derivatives trading industry that includes Contract for differences and financial spread betting.

There are two main types of retail FX forex brokers offering the opportunity for speculative currency trading: forex brokers and dealers or market makers. forex brokers serve as an agent of the customer in the broader FX market, by seeking the best price in the market for a retail order and dealing on behalf of the retail customer. They charge a commission or mark-up in addition to the price obtained in the market. Dealers or market makers, by contrast, typically act as principal in the transaction versus the retail customer, and quote a price they are willing to deal at.