Answer:The type of art material the draeing was made with.
Explanation:
Here is a list of the different drawing mediums and different advantages of those mediums:
Pencil: drawing pencils comes in different "thicknesses"/"boldness". (2H, HB, 4B, 8B, etc.) This is nice for shading and realistic pictures, or simple sketches.
Color pencil: professional color pencils are really nice quality and allows one to push hard on the pencil and create smooth, powerful texture. This can be nice for realistic art pieces with color, or interesting abstract pieces. Again, pencils come with the advantage of control.
Pen: biggest advantage with pen is detail. One can combine pen with other mediums such as watercolor or ink wash to create really nice mix media pieces. I've notice some very talented artists able to use ballpoint pen and create hyper realistic drawing. (pens allow for an amazing ability of control)
Charcoal: charcoal's unique texture is its best advantage. While the messier of mediums, blending charcoal can create smooth and realistic pieces, such as still lifes. Charcoal's texture and line quality is also nice for gesture drawings.
Pastel: there is no limit to what pastels can do. The two types of pastels are oil pastel and chalk pastel, both with very different textures. It is very hard to blend oil pastels, but easy to blend chalk pastels. Oil pastels are also thicker.
Watercolor: watercolor paints are very light and have interesting texture. One thing about watercolor is that without experience, it is hard to control. But with the right touch, watercolor pieces are be beautiful.
Gouache Watercolors: same type of paint as watercolors but thicker and bolder.
Acrylic: acrylics are a very thick paint. With acrylic you have the ability to water it down like a wash, or leave it in its naturally bold texture.
Oil paint: oil paints are a very, VERY thick paint. Much thicker than acrylic. Also much harder to water down. (Would have to use a special solvent). Can provide interesting texture.
Finally, the newest medium of drawing:
Digital Art: done with art software and art tablet. Completely different type of art style. Many put this in its own category of technical art.