IAP or 'In App Purchase' is a payment of real money for in game benefits. Currently, players can buy 3 things from the 'in app store'. Gold (Order&Chaos's currency), Rune Stones and Membership can be purchased. Rune stones can be used to provide extra experience points and bonuses while killing monsters for a limited time. Also, amongst other things, they can buy vanity items and the ability to respawn where you died. Gold is the main currency in Order and Chaos Online and is the most popular IAP service.