Final answer:
Grace and her fiancé's behavior of visiting stores to check out merchandise but then purchasing online is known as showrooming. This consumer trend often involves comparing prices on mobile devices and opting for online retailers that can offer lower prices due to economies of scale and lower overhead costs.
Step-by-step explanation:
When Grace and her fiancé visit furniture stores to gather information on their smartphones, but ultimately decide to purchase their favorite items online, this behavior is referred to as showrooming. Showrooming is the practice of examining merchandise in a traditional brick-and-mortar retail store or other offline setting, and then buying it online, sometimes at a lower price. The practice of showrooming has been facilitated by the convenience of mobile internet connectivity, allowing customers to compare prices and purchase items from online retailers like Amazon, which maintains massive inventories in large warehouses and leverages economies of scale to offer competitive pricing.