The term "design" is a very wide-ranging and an ambiguous term. It is wide-ranging because it covers a wide range of categories in design. It is ambiguous because when someone says that he/she is a designer, it not a clear answer as there are number of responsibilities that are incorporated under the umbrella of term "designer".
In e-Commerce industry, a bad design and cluttered website can easily drive away the potential customers from your online store. So, while planning the design of the store site, it is very important for store owners to understand the difference between user-experience and user-interface. If a store owner wants to hire a person to work on the design of the website and do not understand the difference between UI and UX; he/she might end up hiring a wrong person for the job.