Drawing is the process of recording on a surface what you see before your eyes or in your imagination.
One thing that differentiates drawing from Painting by the fact that in drawing an artist uses pure colors and cannot mix them (before application) one with another, while in painting the common practice of creating a new color is by mixing.
Drawing media mix on the surface because of direct chemical interaction, overlaying (also known as glazing) so that the light reflected from the surface comes through, or by just being close enough that the eye "mixes" them.
The most common types of drawing are pencil, pastels or pen and ink drawings. Many drawing materials are not water or oil based and can be applied without any preparations. There are water based drawing media (e.g., "watercolor pencils") which can be drawn with as ordinary pencils, then washed over with a wet brush to get different effects. There are also oil-based pastels.
Interestingly enough, the "modern" art community has started referring to pastel and colored pencil compositions as paintings, just to muddy the waters...