What is the meaning of Incentive Stock Option (ISO)?

Incentive Stock Option (ISO) is an Option that has met certain tax requirements entitling the optionee to favorable tax treatment. Such an option is free from regular tax at the date of grant and the date of exercise (when a non-qualified option would become taxable). If two holding period tests are met (two years between grant date and sale date and one year between the exercise date and sale date), the profit on the option qualifies as a long term capital gain rather than ordinary income. If the holding periods are not met, there has been a "disqualifying disposition".