Sales officer

A sale is the pinnacle activity involved in selling products or services in return for money or other compensation. It is an act of completion of a commercial activity.
A sale is completed by the seller, the owner of the goods. It starts with consent (or agreement) to an acquisition or appropriation or request followed by the passing of title (property or ownership) in the item and the application and due settlement of a price, the obligation for which arises due to the seller's requirement to pass ownership, being a price the seller is happy to part with ownership of or any claim upon the item. The purchaser, though a party to the sale, does not execute the sale, only the seller does that. To be precise the sale completes prior to the payment and gives rise to the obligation of payment. If the seller completes the first two above stages (consent and passing ownership) of the sale prior to settlement of the price the sale is still valid and gives rise to an obligation to pay.
This is where the salesman represents both parties in the sale and acts as a mediator for the transaction. The role of the salesman here is to over see that both parties receive an honest and fair deal, and is responsible to both.
This is where the salesperson doesn't represent either party, but handles the transaction only. This is where the seller owes no responsibility to either party getting a fair or honest deal, just that all of the papers are handled properly.