A designer's creative tools are the elements of line, shape, space, color, value, texture, and typography. Imagine a giant Sycamore tree. The tree can be represented as thick lines and solid branching shapes. Or, sculpted as an imposing three dimensional form.
It can be photographed as a tightly cropped image of mottled bark in a range of colors, values, and textures. Perhaps the Sycamore's peeling trunk exposes carved initials—typography from days past.
Lines give character to your composition and are a designer's most basic tool. Lines can be circular, straight, wispy, sharp, thick, thin, zigzag, or irregular. Lines possess character. They may appear as strong, serious marks, or playful, meandering doodles.
Compare the endless varieties of lines in leaves and tree bark, versus the horizontal and vertical lines of modern architecture. Contrast the loose, flowing line of a calligraphy brush with a rule drawn by a precise, technical pencil.
Graphic designers emphasize line quality to expand an underlying concept, convey a mood, or reinforce a style.
Lines keep things moving. They introduce your heading, add visual accent, and invite your reader to continue scanning your page.