What is the difference between American & European style options?
If you own(bought) an American style option, you can exercise your right to buy (in case of call options) or right to sell (in case of put options) underlying asset anytime between the purchase date and expiry date. If you own(bought) an European style option, you can exercise your right to buy (in case of call options) or right to sell (in case of put options) underlying asset only on the expiry date.