If goods are selected with the intention of using them in performing the contract, with the mutual consent of the buyer and the seller, then it is called appropriation of goods
Conditional appropriation means that the goods are appropriated to the contract subject to fulfilment of certain conditions by the parties. eg payment of advance by the buyer
Unconditional appropriation means that the goods are appropriated to the contract are not subject to any condition precedent to be fulfilled by the parties