These options can be excercised any time before expiration. This is opposed to a European Option, which can only be excercised at expiration.
Taking on multiple positions in a security in order to profit from a mispricing in a financial instrument. Many people will use options to construct a position in the underlying security to do this.
At The Money
This is when a put or call options strike is the same as the underlying price. A call option with a strike price of 25 is "at the money" when the underlying stock, etf or index is trading at 25.