When a direct booking request (not a reservation!) is submitted, an authorization hold will be placed on your credit card for the amount of the booking total to ensure there are enough funds available in the account. A hold is often stated as a "pending" or "processing" transaction in your bank statement. The card you have on file will not be charged in full until the direct booking request is accepted by the host.
In case of a reservation, the host has to accept the reservation and then you have 72 hours (only workdays) to book the room. Only if the room is finally booked, you will get charged for it.
If you choose "paying by invoice" as your payment method, you have time to pay the full amount until the day before the event.
We highly recommend that you only submit a booking when you are certain that a cancellation is very unlikely.