Although the terms interior decorator and interior design are sometimes used interchangeably, each discipline exhibits a distinct difference in its scope.
This explanation my help.
An interior designer combines education and experience with aesthetic vision in order to develop design solutions that take in to account the structure of a space, the needs of the occupants, and the style that suits both. Interior design services include space planning, placement of non-load bearing interior walls, specifications of furniture, fabrics and finishes, and compliance with building, fire, and life safety codes. Interior designers create and enhance interior spaces including offices, restaurants, hotels, schools, hospitals, private residences and more.
An interior decorator is a paid consultant on the selection of finishes, such as wallpaper, window treatments, fabrics, furniture, flooring, and fixtures to an interior space. Interior decorators select the items in a room so that it is attractive, easy to use, and functions well within the existing architecture. Interior decorators do not deal with building codes, fire codes and/or occupancy of a space.