Options on futures began trading in 1983. Today, puts and calls on agricultural, metal, and financial (foreign currency, interest-rate and stock index) futures are traded by open outcry in designated pits. These options pits are usually located near those where the underlying futures trade. Many of the features that apply to stock options apply to futures options.
Sometimes corporations enter the forex market in order to hedge their profits. A US company with extensive operations in Mexico, for example, may enter into a futures contracts on US dollars. So, when it comes time to bring those Mexican profits home, the profits earned in pesos will not be subject to unexpected currency fluctuations. The futures contract is a way of securing an exchange rate and eliminating the risk that peso will lose value versus the dollar, making those profits worth less in dollars.
The currency market, or foreign exchange market ("forex"), was created to facilitate the exchange of currency that becomes necessary as the result of foreign trade. That is, when an entity in one country sells something to an entity in another country, the seller earns that foreign currency. When China sells t-shirts to Walmart, for example, China earns US dollars. When Toyota wants to build a factory in the US, it needs dollars. It may get those from its local bank, which in turn will obtain them in the international currency market. This market exists to facilitate these types of exchanges.
Conversely, a put option is a contract that gives the investor the right to sell a certain amount of shares (again, typically 100 per contract) of a certain security or commodity at a specified price over a certain amount of time. Just like call options, a put option allows the trader the right (but not obligation) to sell a security by the contract's expiration date.
Spreads use two or more options positions of the same class. They combine having a market opinion (speculation) with limiting losses (hedging). Spreads often limit potential upside as well. Yet these strategies can still be desirable since they usually cost less when compared to a single options leg. Vertical spreads involve selling one option to buy another. Generally, the second option is the same type and same expiration, but a different strike.
When buying or selling options, the investor or trader has the right to exercise that option at any point up until the expiration date - so simply buying or selling an option doesn't mean you actually have to exercise it at the buy/sell point. Because of this system, options are considered derivative securities - which means their price is derived from something else (in this case, from the value of assets like the market, securities or other underlying instruments). For this reason, options are often considered less risky than stocks (if used correctly).