design principles-
I'm borrowing this simple explaination of what they do from my good friend and art instructor, Bob Kennedy. I believe he created this as a simple handout for his students to give them a quick frame of reference .
THE ELEMENTS OF DESIGN
The Elements of Design are the things that artists and designers work with to create a design, or composition. The Elements are: line, shape, space, value, color, and texture.
Line … The Graphic Unifier. Curved, Straight, Directional Thrust: Horizontal, Vertical, and DiagonalA curved line is dynamic, ever changing, and more natural, than the straight line, which is more static in character. Direction, while often listed as a separate element, is technically a part of the element "line". The diagonal line is more dynamic and is quicker to draw the eye. It can be used to create movement and depth. Horizontal lines are more static and tranquil therefore calmer, more passive. Vertical lines evoke strength, power, but less dynamic than diagonals.
Shape … Natural, Geometric. Positive and Negative. (The Golden Mean)Geometric shapes are more passive, decorative, and static than organic shapes. Repeated shapes can be used to create movement. Repeating geometric shapes increases the decorative effect. Look beyond the obvious shapes of heads, bodies, buildings, etc., and view your subject as abstract shapes. Change many of the obvious shapes and create new more interesting shapes. Try to find interlocking shapes. Keep the background shapes in the background, but look for places to connect the foreground and background.
Space / Size … Large, Medium, Small. Proportion or Scale. (The Golden Mean)The comparative relation between things. Employ large, medium, small concept. Size can be used to make things appear nearer and of greater importance. Size relationships can be used to create depth (Perspective).
Value … Light, Dark. (Value Patterns)Value can be used to create mood, i.e. dark and mysterious, light and airy, gray and dull. High contrast in value moves things forward; low contrast makes them recede. (Arial Perspective)
Color … Hue, Chorma, and Value. Hue is the specific name of a color, red, yellow, blue (primary colors). (The Color Wheel)Chroma, also called saturation, often called intensity, refers to a colors strength or weakness, bright or grayed.Color Value refers to the lightness or darkness of the color, not to its intensity or to a specific hue.
Texture … Rough, Smooth, Soft, Hard.Texture shows at the edges and in the play of light and shadow on the surface.A COMPOSITION is an arrangement of all the elements, which achieves a unified whole. But alas, it is merely a tool to create form and content. Content relates to human emotion and the intellect and is the end result of the reasons for painting. Design is a means to that end.See: Types of Compositions and A Simple Approach to Good Design
ATTRIBUTES are defined as the qualities that the art or design conveys to the observer.Emotional … Active, PassiveEsthetic … Realistic, Impressionistic, Abstract, DecorativeSpatial … Depth, Flat

THE PRINCIPLES OF DESIGN
The Principles of Design are achieved through the use of the Elements of Design. Each principle applies to each element and to the composition as a whole. The principles are unity, harmony, balance, rhythm, contrast, dominance, and gradation.
Unity … Echoes of all elements relating. All things are connected and belong to the whole. The distinguishable units and elements seem to belong to each other so that each contributes to the functioning of the whole. The work is complete when no element can be changed without detracting from the whole.
Harmony … Within each element and as a whole.Harmony can affect the emotional response to the composition.
Balance … With the "weights" of the segments of each element.An equilibrium of similar, opposing, or contrasting elements that together create a unified whole. Forms of balance: Asymmetrical Balance and Symmetrical Balance.
Rhythm … Variety and Repetition.Variety within the design of all the elements and principles, along with, the regular repetition of particular elements or stresses, also, the suggestion of motion by recurrent form.
Contrast … Alternation.Provide contrast within each element i.e. light, dark; soft, hard; warm, cool, etc.
Dominance … Within each element. (Center of Interest and Focal Point)Dominance provides emphasis. The center of interest is the area within the work to which the eye is drawn. The Focal Point is the point within the center of interest that catches the eye. It is this area and point that the artist emphasizes through the use of the elements.
Gradation … Modeling, (the 3-D effect), Transitions.Used in modeling or producing a three dimensional effect and in transitional effects. Gradation of detail from foreground to background. (Ariel Perspective)