A contract that is agreed to by the Vendor and the Buyer, but where one or more conditions need to be met, usually within a specified time period, by either or both parties, e.g. it is subject to the purchaser raising finance within a few days or subject to the lawyers consent of the title etc.
A contract hat contains a number of conditions that both parties must comply with. An insurance policy is a conditional contract.
A Contract of Purchase and Sale that has been agreed to by both buyer and seller, but has conditions to be removed before the contract becomes firm and binding. The buyer is in control of the sale at this point and has the option of not proceeding with the contract if the conditions are not met. The seller can not accept another offer except as a back-up offer.