The key differences between a sale and an agreement to sell are: 1) In a sale, the property of goods passes immediately from the seller to the buyer, making the buyer the new owner, whereas an agreement to sell involves transfer of property at a future time or when conditions are met. 2) A sale can only involve existing and specific goods, while an agreement to sell usually involves future or contingent goods. 3) In a sale, if the goods are destroyed, the loss falls on the buyer even if still in the seller's possession, but an agreement to sell does not immediately transfer risks.