What are the main differences between the "Elements of Art" and the "Principles of Design"?

The elements of art are line, shape, form, texture, value, space, and color. The principles of design (also called the principles of art) are balance, harmony, contrast, emphasis, movement, repetition, rhythm, proportion, and unity.

In short, elements are things that make the design. Principles are rules, guidelines, and philosophies, that govern the design.