Employee stock ownership plans are just options that could be purchased at a specified price before the exercise date. An organization grants ESOPs as a right and not as an obligation , to its employees, directors and officers for buying a specified number of shares of the company at a defined price exercise price after the exercise period a certain number of years. Before an employee could exercise his option , he needs to go through the pre-defined vesting period which implies that the employee has to work for the organization until a part or the entire stock options could be exercised.