Exercise price is usually lower than the prevailing FMV of the stock. An employer and employee agree on ESOP terms on the grant date. Once the employee has fulfilled the conditions or the relevant time period has elapsed, these employee stock options are vested. At this time the employee can exercise them or put simply – buy them. The employee is allowed some time period during which this option to buy can be exercised. Once the employee decides to buy, these stock options are allotted to him at an exercise price which is usually lower than the FMV of the stock. Of course, the employee can choose not to exercise his option.