A bill of sale is a legal document made by the seller for the purchaser/buyer that reports the time and place of sale, as well as the value received (money or otherwise). This written instrument transfers the title of personal property from the seller to the buyer.
A bill of sale can be "absolute" or "conditional". An absolute bill of sale is simply documents the transfer of personal property: it is equivalent to a contract of sale of goods under common law. A conditional bill of sale also documents transfer of property but with the condition of security for the payment due. It therefore creates security in favor of the grantee, the buyer, because the grantee is given the right of seizure.