The market section is the central hub of control for DragonVale World. It is the place where dragons, habitats, decorations, and buildings. Treasure from the App Store, Google Play, or Amazon Appstore via In-App Purchases can be bought for real currency.
In the Treasure section of the market, gems, can be purchased for real currency. It is the only section in the entire game where real currency can be spent and there is a confirmation screen before a purchase is made. In case you have entered your password anywhere when playing the game, make sure the "In-App Purchases" slider is set to "OFF" in the settings on your device.