What are some types of line, and what are their purposes? (site 1)?

Lines can be horizontal, vertical, diagonal, straight, curved, thick or thin. Many types of line are contour and cross-hatching. Their purposes are: Contour lines are to define an edge and will help you define an image, whereas cross-hatching represents value and shows light and shadow. Lines can help artists guide eyes through the composition, communicating information through detail and direction. Lines can create building blocks such as visual elements: shapes, 3-D space, color is light reflected off objects, and texture is the feel, appearance, or consistency of a surface.

Explanation:

This is the hard one on Edgen without going through carefully, so it will give you 100% :)