The interior design have a sence of design and structure. He interfaces with the architect in order to resolve technical issue such as plumbing, ventilation, furnishing, electrical circuts etc. Now a days the interior designer also ensure that the structure is eco friendly and in harmony with the nature.
Interior decorators are the creative artists who have no knowledge of architectonics. They are mainly concern with the superficial details like the color scheme of the rooms, choice of the floor tiles and matching wall papers, advising for suitable fabrics for curtains etc. Thus while the interior designer is concerned with the formalistic aspects of structure, the decorator is bothered by the content and image they convey.