An option is a contract to buy or sell a specific financial product known as the option’s underlying instrument or underlying interest. Option buyers are charged an amount called a “premium” by the sellers. Should market prices be unfavorable for option holders, they will let the option expire worthless, thus ensuring the losses are not higher than the premium. In contrast, option sellers (option writers) assume greater risk than the option buyers, which is why they demand this premium.
Options trading is typically a “long”, meaning you are buying the option with the hope of the price going up (in which case you would buy a call option). However, even if you buy a put option (right to sell the security), you are still buying a long option. Shorting an option is selling that option, but the profits of the sale are limited to the premium of the option, and the risk is unlimited.
A Call option gives the contract owner/holder the right to buy the underlying stock at a specified price by the expiration date. Calls are usually purchased when you expect that the price of the underlying stock may go up.
A Put option gives the contract owner/holder the right to sell the underlying stock at a specified price by the expiration date. Puts are usually bought when you expect that the price of the underlying stock may go down.