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.
Strike Price: This is the price at which you could buy or sell the underlying futures contract. The strike price is the insurance price. Think of it this way: The difference between a current market price and the strike price is similar to the deductible in other forms of insurance. As an example, a December $3.50 corn call allows you to buy a December futures contract at $3.50 anytime before the option expires. Most traders do not convert options to futures positions; they close the option position before expiration.
The market value of that home may have doubled to $800,000. But because the down payment locked in a pre-determined price, the buyer pays $400,000. Now, in an alternate scenario, say the zoning approval doesn’t come through until year four. This is one year past the expiration of this option. Now the home buyer must pay the market price because the contract has expired. In either case, the developer keeps the original $20,000 collected.

Purchasing a call option is essentially betting that the price of the share of security (like a stock or index) will go up over the course of a predetermined amount of time. For instance, if you buy a call option for Alphabet (GOOG) at, say, $1,500 and are feeling bullish about the stock, you are predicting that the share price for Alphabet will increase. 
However, for put options (right to sell), the opposite is true - with strike prices below the current share price being considered "out of the money" and vice versa. And, what's more important - any "out of the money" options (whether call or put options) are worthless at expiration (so you really want to have an "in the money" option when trading on the stock market). 
An option is a contract that allows (but doesn't require) an investor to buy or sell an underlying instrument like a security, ETF or even index at a predetermined price over a certain period of time. Buying and selling options is done on the options market, which trades contracts based on securities. Buying an option that allows you to buy shares at a later time is called a "call option," whereas buying an option that allows you to sell shares at a later time is called a "put option." 
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