The expiry type allows you to elect how long you want your order to be in the market.
The order is open (in market) for the day the order was placed and will expire once the market has closed for trading on that day.
Good Until Date
Good until date allows the order to remain open (in market) until the predetermined date, which gives you more chances of the order being filled. If the order is not filled before the predetermined date the order will be cancelled.