Internal decorating is the art of accenting and modifying the architectural achievements of a space for the generation of pleasing aesthetic experiences. It can involve the remodelling of a given space so it's not just the design of surfaces and use of everything from mirrors to room dividers to break up a space or amplify its presence. Internal decorating ultimately reflects a psychology of design and a principle of shaping spaces to functions and utility. It is an art in its own right of designating fluency Feng Choi or Feng Shui, is an example of early Interior decorating based on principles of assumed meanings implicit to the generation of desired results on the basis of a fusion of superstition based on the assertion of fortuitous results, that some may argue are also pragmatic considerations that have to do with the flow of energies natural to an ergonomics of functional applications, based on cultural dispositions of how to organize space optimally for beneficial results.
Ultimately that definition serves our purpose and Interior decorating is just that the priority of organizing spaces for optimal benefit, in the pursuit of changes in the cultivation of spaces for the manifestation of different priorities. The work space designed to optimize work, the personal space designed to optimize optimal living conditions, even galleries and museum curation, and public space design, is a kind of interior decorating. I hope this answer helps.