Well, here they are - the infamous Elements and Principles of design. The principles are typically the first things that are learned, and they become the foundation of exceptional design. The elements follow as they are the most basic visual components of any room composition. The elements are the materials upon which the principles act, since the principles govern the relationship of the elements themselves. Confused? Let me explain each item independently and we'll see if that helps.
Principles: balance, rhythm, proportion, unity, harmony, emphasis, scale
Balance - the balance within a room will be symmetrical or asymmetrical. It refers to all items in the room: furniture, accessories, window treatments, etc., as they relate to one another in size, weight, and placement.
Rhythm - the repetition of elements in a room. They can be regular, flowing, and/or progressive.
Proportion - the relationship in scale between one element and another within the space
Unity - the relationship between the individual items of a design and the entire composition, the sense of order in a space
Harmony - the relationship between unity, repetition of element, and balance
Emphasis - this is the focal point of the room, the center of interest
Scale - this relates to the size of an object when compared with the size of the space in which it is located
Elements: space, line, form/shape, color, texture
Space - defines the boundaries and limits of the room you are working with
Line - the lines in a room are the second most important thing, with color being the most important. Line refers to the vertical, horizontal, diagonal, and curved edges defined by furniture, architecture, window treatments, etc.
Form/Shape - this refers to the different objects in the room that pertain to the basic shapes such as rectangle, square, triangle, diamond, circle, and oval.
Color - color is the most important facet of a room. It can single-handedly transform the mood and look of any space, and it can psychologically change the temperature as well.
Texture - the texture of every item that is used in a design must be accounted for. The eye and mind can discern texture without the hand even touching it. This element adds depth.