There are two kinds of options: American-style options and European-style options. American options can be exercised at any time up to the maturity of the option, whereas European options are exercised toward the end of the contract.
Exercising options is done by the option buyer. If the buyer exercises a put, he is selling to the option writer the stock. If a call is being exercised, he is buying the stock from the writer.
In both cases, you will have to provide the stocks to the counterparty if the option is exercised. There are two differences. First is the nature of the option. Calls are exercised when the stock spot price exceeds the call's strike price. Puts are exercised when the stock spot price is below the put's strike price. The other is, if you write a call you don't get to decide whether it gets exercised--the buyer does. If you buy a put, the choice to exercise it is yours.
An American put option can be exercised at any time during its life. The European put option can only be exercised at the end of the contract period.
It depends on why you're writing the call. If you're doing it to make money by collecting the premium, and possibly the payment for the stock if the call is exercised, the tradeoff is you will make money but you might not make as much as you could have by selling the stock on the open market if the spot price of the stock when the option is exercised is higher than the strike price plus the premium. If you're doing it to lock in your profits (or as part of a collar), there really isn't a tradeoff--whether the option is exercised or expires worthless, you still make money on the deal.
ESPP is an option given to employees to purchase companys stock out of their after tax wages and salaries at a discounted price. while ESOP is not in lieu of wages/salaries it is in the form of a call option which can be exercised at a predetermined date.
A call option gives the option buyer the right, but not the obligation, to buy a certain amount of stock on or before a certain date for a certain price. A put option gives its buyer the right, but not the obligation, to sell stock on or before a certain date for a certain price. How the options are exercised is another difference. If you bought a put, you're hoping the stock price falls below the strike price--the certain price in the contract. It would make no sense to sell stock for $10 a share if it's $15 now, right? Calls exercise when their stock price goes above the strike price.
In finance, an American option is an option which can be exercised at any date between the issue date and the expiry date.
A Bermudan option is an option in finance which can be exercised at specific dates between the issue date and the expiry date.
You do it twice. The first is when you exercise the option. An ISO has a "strike price" - the price you get to buy the stock at. Stock has a fair market price, which is what everyone else has to pay for it. The spread between the two is used to calculate your Alternative Minimum Tax in the year you exercise the ISO, if you hold the stock at the end of the year. Yes, of course there is an example. You work for Acme, and they gave you an ISO to buy 100,000 shares of stock at $10 per share. On the date you exercised this option, the stock was trading at $11. Subtract $10 from $11, multiply by the 100,000 shares, and you have to tell the IRS about $100,000 in spread. If you hold the stock for at least one year after exercising the stock AND two years after receiving the ISO (which might actually mean you held the stock for two years, if you exercised the ISO right away), the tax you will pay is long-term capital gains tax on the difference between the strike price of the ISO and the price you sold at.
A incentive stock option is a employee stock option that can only be done by employees. This option causes the employees to pay less on their income taxes.
In short, a free stock option is just a stock option that is free. It gives you the right to buy something, regardless of whether you actually buy it or not.
A valuation stock option is an agreement made to offer the option to purchase the stock at a later date. The price of the option is based on the reference price and the value of the asset in which the stock is being purchased.