American options can be exercised at any time between the date of purchase and the expiration date. European options are different from American options in that they can only be exercised at the end of their lives on their expiration date. The distinction between American and European options has nothing to do with geography, only with early exercise. Many options on stock indexes are of the European type. Because the right to exercise early has some value, an American option typically carries a higher premium than an otherwise identical European option. This is because the early exercise feature is desirable and commands a premium.
Call writers and put writers (sellers), however, are obligated to buy or sell if the option expires in-the-money (more on that below). This means that a seller may be required to make good on a promise to buy or sell. It also implies that option sellers have exposure to more, and in some cases, unlimited, risks. This means writers can lose much more than the price of the options premium.
As an example, let's say a farmer is expecting to produce 1,000,000 bushels of soybeans in the next 12 months. Typically, soybean futures contracts include the quantity of 5,000 bushels. The farmer's break-even point on a bushel of soybeans is $10 per bushel meaning $10 is the minimum price needed to cover the costs of producing the soybeans. The farmer sees that a one-year futures contract for soybeans is currently priced at $15 per bushel.
In the case of perishable commodity, the cost of storage is higher than expected future price of a commodity (For ex: TradeINR prefer to sell tomatoes now rather than waiting for 3 more months to get a good price as a cost of storage of tomato is more than price they yield by storing the same). So in this case, the spot prices reflect current supply and demand, not future movements. There spot prices for perishables are more volatile.
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On the other hand, commodity option buyers are exposed to limited risk and unlimited profit potential, but they also face dismal odds of success on each individual speculation. For this reason, we often refer to the practice of buying options in the commodity markets as the purchase of a lottery ticket. It probably won’t pay off but if it does the potential gain is considerable. Conversely to the commodity option seller, an option buyer views the position as an asset (not a liability) until it is sold or expires. This is because any long option held in a commodity trading account has the potential to provide a return to the trader, even if that potential is small.
For example, if you bought a long call option (remember, a call option is a contract that gives you the right to buy shares later on) for 100 shares of Microsoft stock at $110 per share for December 1, you would have the right to buy 100 shares of that stock at $110 per share regardless of if the stock price changed or not by December 1. For this long call option, you would be expecting the price of Microsoft to increase, thereby letting you reap the profits when you are able to buy it at a cheaper cost than its market value. However, if you decide not to exercise that right to buy the shares, you would only be losing the premium you paid for the option since you aren't obligated to buy any shares. 
Traders that are willing to accept considerable amounts of risk with the prospects of limited reward, can write (or sell) options, collecting the premium and taking advantage of the well-known belief that more options than not expire worthless. The premium collected by a commodity option seller is seen as a liability until the option is either offset (by buying it back), or it expires. This is because as long as the option position is open (the trader is short the commodity option), there is substantial risk exposure. Should the futures price trade beyond the strike price of the option, the risk is similar to holding a commodity futures contract outright.
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).