A pending charge is the authorization of funds for your credit card. When you place an order with a credit card, we must check that the funds are available before we release your order. We authorize for an amount 10% higher than the total of the order in case taxes need to be charged.
Sometimes this authorization shows up on your account. How long it stays there is up to your credit card company. It can be anywhere from 1-2 weeks.
This authorization will disappear and be replaced by the actual charge when your order ships and taxes are known. If your order ships quickly, you may still see both the authorization and the charge on your credit card statement until the authorization disappears.