Generally, writing pencils will have eraser tops, and have hardness grades like No. 1, No. 2, and No. 3 (No. 2 being the grade most commonly available). Graphite pencils for drawing typically do not have eraser tops, and they have hardness grades ranging from 9H (very hard) through HB (equivalent to a No. 2) and on to B grades like B (somewhat soft), 6B (very soft), or higher. Please note that hardness grades are not standardized, so the softness of a pencil, even of the same grade, will vary by manufacturer.
For delicate cores such as those found in pastel, charcoal, and colored pencils, we generally recommend a handheld sharpener. We do offer some electric and battery-operated sharpeners that are compatible with colored pencils—just remember to occasionally sharpen a graphite pencil to keep wax from gumming up the sharpener. These types of pencils may also have a larger-than-standard diameter, so it's important to make sure the sharpener you choose will accommodate the pencils you have.
For graphite pencils, almost any sharpener will be appropriate, including so-called "long-point" sharpeners. These provide very sharp points on slim-cored graphite pencils that quickly become unwieldy on thicker-cored color, pastel, or charcoal cores.