In order to trade stock options, you need to know a few terms:
Expiration date. Duration of the usefulness of an option contract
Strike price. How much the contract may be executed for at the agreed upon pricing
Option premium. Intrinsic and extrinsic values are included in the cost of an option.
Intrinsic (in-the-money) value. The difference in price between the exercise price of an option and the underlying stock
Extrinsic value. Time and volatility are used to determine the contract's value.
Implied volatility. An indicator of the anticipated or predicted volatility in a stock over a certain period of time.

A stock option is a type of security that gives the holder the right to purchase shares in the underlying company at a predetermined price (known as the strike price) for a certain length of time (called an expiry date).  They are often issued by employers to employees as part of an employee share-based compensation package.  The value of an option can change based on what happens with regards to the price of the underlying stock.