Final answer:
An impulse buy is an unplanned decision to purchase an item just prior to a transaction, often influenced by emotions or environmental stimuli like product placement.
Step-by-step explanation:
The type of purchase BEST described as a customer's unplanned decision to buy an item just prior to the transaction is known as an impulse buy. Impulse buying occurs when a buyer selects an item on the spur of the moment, typically influenced by emotions or feelings rather than careful thought or planning. Such purchases are often made in response to stimuli in the purchasing environment, such as attractive item displays or promotional signs.
An example of impulse buying could be grabbing a candy bar from the checkout aisle at a grocery store. The buyer may not have planned to purchase candy but decides to do so right before paying for their other grocery items. This type of purchasing behavior is influenced by factors such as convenience, the appeal of the product, and sometimes, the strategic placement of items where consumers are likely to make last-minute decisions.
Another example could be adding a pair of sunglasses to a purchase at a clothing store because they were positioned near the cash register and caught the customer's eye. The decision to purchase is made quickly, without prior intention, and is often driven by visual appeal or the desire for immediate satisfaction.