An offer is just that - an offer. If it is not accepted by the seller within the time limit you set, your offer is void.
Most offers are contingent offers - that is, they become void unless certain things happen.
All offers are contingent upon:
If any of the contingencies in an offer are not met within the time frame you set, the offer is void and your deposit is returned to you.
Most offers are also conditioned upon certain promises
by the seller, such as: