By clicking this tab, you can enter the bank feature. Here you can buy helix and cel, starter packs, advantage packs, savings packs, flotsam doublers, and premium accounts. While it is not necessary to buy these items to play the game, they can make it easier. You can also exchange helix for cel in this area. Most people buy helix or wait for what's known as a "Happy Hour", or the rare "Mega Happy Hour" to buy helix, where the amount of helix you get is doubled in a happy hour and tripled in a mega happy hour.
There's a variety of pay options, ranging from cash to a pre-paid game card, to a credit card. All their transactions are done via a secure SSL conection to protect your data.