An Option Contract gives a buyer the right (which is not an obligation) to buy/sell securities at a pre-determined price and date. The option is European style.
The buyer of the option contract is not required to buy/sell the security if they decide against it. They are however obligated in case of a forward contract.
This optionality comes with a price i.e. option premium which is generally paid upfront. Tenure, Volatility and Strike Price drive the Option Premium.