Lines are one of the basic building blocks of design. It is a mark made by a tool as it is drawn across a surface.
The tool can be anything - pencil, pointed brush, a computer and mouse, cotton swab.
Line type - straight, curving, or angular.
Line direction - relationship to the page - horizontal, vertical, diagonal.
Line quality - how a line is drawn - delicate, bold, broken, thick ,thin, regular, changing.