This information is not commonly discussed amongst the buyers but I think it's important that you know so you don't freak out when something looks odd.
In the past we have had the option enabled when a card is processed to pre authorize that amount and leave the card open so the amount can be adjusted if needed for shipping, taxes etc...
At the time this was our only option but a few years back we implemented a new service that took your information and created it as a token and send the information to use to process once the order is received so the end used only sees one charge which is the final charge eliminating confusions sometimes created with an authorization and final charge that may show up as a double charge on your statement for up to 48 hrs. So what happens now is you will not see a charge on your card immediately as our store does not ping the credit card provider to make sure that the information is accurate or that funds our available. This can create another problem of expired cards being used, a fraud alert, or there being insufficient funds in the account.
So make sure that the card being used will process at the time we tender the order and if not we will make every attempt to contact you but it can delay your order
So regardless of which type of card you use we have eliminated any issues of a double charge showing up on your statement as the charge is only sent through one time. The above information only holds true for the credit card placeholder that you see in checkout, if you choose to use PayPal to process your card the pre-authorization cycle still exist and I highly advise against using a debit card with PayPal because if the final total is altered it can cause a pre-authorization for the amount seen in checkout and a different toal when tendered for a final charge if shipping needed to change or tax added.