Here you can trade wishes that you have earned throughout the game, for various rewards. You can earn wishes by completing certain achievements, or by completing offers. You may also buy wishes using paypal and other various ways.
Sometimes after completing an offer you may not recieve your wishes. This happens often but is easily fixed. If you click on the "missing wishes" button on the genie tab you can file a report with the confirmation e-mail that you received from your offer.
Normally you can trade your wishes for three things. Money. A mercenary. Or Mana. With money the equation goes, your level times 10,000 equals how much gold you get for 10 wishes. For a mercenary the deal goes, 1 mercenary for 20 wishes. For mana the deal goes, 10 mana for 10 wishes.
As you progress through the game these wishes will seem less useful so I recommend using them while you are a lower level to help you progress through the game quicker.