Mice are not very precise for drawing, so a graphics tablet is often an important tool for most digital illustrators, because it allows the user to make a mark easily in any direction, in a way that reflects the natural or "lively" line made by the human hand.
In addition to flexibility of movement, an industry-standard digital drawing tablet has a pressure-sensitive surface, allowing the illustrator to make marks that vary from faint to bold, and from thin to broad, similar to how one would work with a brush.
With a bitmap application, the content is stored digitally in fixed rows and columns of pixels, which can be created in separate layers for more easily isolating and manipulating different parts of the image.
Painting tools allow the easy creation of "fuzzy" imagery, including effects such as glows and soft shadows, and textures such as fur, velvet, stone and skin, and are heavily used in photo-retouching.
Drawing tools typically create precise lines, shapes and patterns with well-defined edges and are superb for working with complex constructions such as maps and typography.