Are you using the terms "interior designer" and "interior decorator" interchangeably? Do you REALLY Know that there is a HUGE difference in what these two titles mean in the professional sense; and, in fact, if used incorrectly, you could be insulting someone! Read this post to learn more of what you need to know.
Form is made up of points, lines, planes, volumes, and shapes; these then become the starting point to your design. When looking for a new home, or remodeling your current one, the form is one of the most important aspects to consider, but, can be manipulated through design and decoration.