What is a "hold" or "preauthorization"?

When making a purchase, merchants will do a “hold” or "preauthorization" for the estimated total price of your transaction. This will appear as a pending transaction and will reduce your available balance by the "Authorized Amount". The "preauthorization" expires once the merchant processes the "Final Transaction Amount". This could take several business days, and during this period you will not be able to use any value in which there is a "hold". See the Cardholder Agreement “Using Your Card/Features” for details