"Contour" is a French word that means outline. Just as the name implies,
 contour drawing is basically drawing an outline of an image to
 emphasize mass and volume instead of focusing on the little details.
 Sometimes contour drawing can convey three dimensional perspective.
 Because of this, factors such as length, width, thickness, and
 depth are important as well. This technique is typically done
 without picking up the pencil.

 Hatching is technique that focuses heavily on detail, especially shading.
 The shading, however, is usually done by drawing lines parallel to one
 another. This is called linear hatching.
 Sometimes, though, the lines drawn can overlap each other at different
 angles. This is called cross-hatching.
 Lines can also be curved to give the appearance of light in the image.
 This form is called contoured hatching.

 Stippling is similar to hatching, but the biggest difference is that
 stippling uses dots for shading instead of lines. The density of the
 dots vary throughout the image.
 The dots are drawn using a pigment of a single color and can be made
 lighter or denser, depending on the density of the pigment.
 Most of the time, stippling is used to draw flowers and plants.

 This technique, also known as a "masking effect," is a technique that
 is used most often in comic books, graphic novels, video games, and
 sometimes animation. Masking is all about creating a detailed
 background that is used behind a more simple character design in
 order to easily render and identify the characters.

 Scribbling, also known as doodling, is one of the most common forms
 of drawing. These doodles are simple drawings that can sometimes
 have meaning or can just be drawn out of boredom. Doodles are most
 commonly found in school notebooks drawn by drawn by students who
 were either daydreaming or simply lost interest in class.
 This type of drawing can be done by pretty much anyone, as long
 as they have paper, pencil, and desire to draw.