Pay a “premium” wherever you buy a commodity option. Let's say you purchase a “call” option on 100 bushels of corn, and the premium is $2 per bushel. You will pay $200 for the right to exercise your option until it expires. That is your only cost to purchase the option, except for whatever commission you had to pay to your brokerage company. Even if you choose not to exercise the option before it expires, your investment will be limited to the $200 premium plus commission.
Trading in commodity futures contracts can be very risky for the inexperienced. The high degree of leverage used with commodity futures can amplify gains, but losses can be amplified as well. If a futures contract position is losing money, the broker can initiate a margin call, which is a demand for additional funds to shore up the account. Further, the broker will usually have to approve an account to trade on margins before they can enter into contracts.

An equity option allows investors to fix the price for a specific period of time at which an investor can purchase or sell 100 shares of an equity for a premium (price), which is only a percentage of what one would pay to own the equity outright. This allows option investors to leverage their investment power while increasing their potential reward from an equity’s price movements.

In terms of valuing option contracts, it is essentially all about determining the probabilities of future price events. The more likely something is to occur, the more expensive an option would be that profits from that event. For instance, a call value goes up as the stock (underlying) goes up. This is the key to understanding the relative value of options.
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.
Covered calls can make you money when the stock price increases or stays pretty constant over the time of the option contract. However, you could lose money with this kind of trade if the stock price falls too much (but can actually still make money if it only falls a little bit). But by using this strategy, you are actually protecting your investment from decreases in share price while giving yourself the opportunity to make money while the stock price is flat. 
So, call options are also much like insurance - you are paying for a contract that expires at a set time but allows you to purchase a security (like a stock) at a predetermined price (which won't go up even if the price of the stock on the market does). However, you will have to renew your option (typically on a weekly, monthly or quarterly basis). For this reason, options are always experiencing what's called time decay - meaning their value decays over time.