An option is a financial product belonging to the category of derivatives. An option gives you the right to buy or sell at a pre-agreed price what is called an underlying asset. This underlying security can be a stock, bond or commodity, or any other asset.
Note that if an option allows you to buy something, it is a call option. On the other hand, if an option allows you to sell something, it is a put option.
The right to buy or sell bestowed by an option is limited in time. The maturity date is the date until which an option can be exercised.