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.
If there’s a company you’ve had your eye on and you believe the stock price is going to rise, a “call” option gives you the right to purchase shares at a specified price at a later date. If your prediction pans out you get to buy the stock for less than it’s selling for on the open market. If it doesn’t, your financial losses are limited to the price of the contract.
When purchasing put options, you are expecting the price of the underlying security to go down over time (so, you're bearish on the stock). For example, if you are purchasing a put option on the S&P 500 index with a current value of $2,100 per share, you are being bearish about the stock market and are assuming the S&P 500 will decline in value over a given period of time (maybe to sit at $1,700). In this case, because you purchased the put option when the index was at $2,100 per share (assuming the strike price was at or in the money), you would be able to sell the option at that same price (not the new, lower price). This would equal a nice "cha-ching" for you as an investor.
An option's price, its premium, tracks the price of its underlying futures contract which, in turn, tracks the price of the underlying cash. Therefore, the March T-bond option premium tracks the March T-bond futures price. The December S&P 500 index option follows the December S&P 500 index futures. The May soybean option tracks the May soybean futures contract. Because option prices track futures prices, speculators can use them to take advantage of price changes in the underlying commodity, and hedgers can protect their cash positions with them. Speculators can take outright positions in options. Options can also be used in hedging strategies with futures and cash positions.
The fee you are paying to buy the call option is called the premium (it's essentially the cost of buying the contract which will allow you to eventually buy the stock or security). In this sense, the premium of the call option is sort of like a down-payment like you would place on a house or car. When purchasing a call option, you agree with the seller on a strike price and are given the option to buy the security at a predetermined price (which doesn't change until the contract expires).