Sale and Agreement to sell are two different things. the legal incidents of the two are vastly different. the basic different has been given under section 4 (3) of the Sale of Goods Act 1930.
According to Section 4(3) where under contract of sale the property in goods transferred from the seller to buyer the contract is called sale, Transfer of Property in goods take place at future time are subject to some condition there after to be fulfilled the contract is called an agreement to sell.