Pencils are writing utensils commonly used in schools. They work by having lead write onto the paper. Pencils are among the few writing utensils that can be erased.
Pens are the utensil of choice for most people. It is much easier to write with pens, and they use ink not lead, so they cannot be erased. Pens work by putting ink onto the paper using a ball.
Highlighters are used to mark certain text or areas of the page, but still be able to read what is beneath it. The ink of a highlighter is usually bright so as to attract the eye to it and make it easier to read what is beneath it. It works my putting ink onto the paper.
Sharpies are permanent markers. They are made to wite in places that ink from other writing utensils will not stay. They are many different kinds of sharpies, including normal, wide, extra wide, thin, extra thin, and sharpie pen. They work by putting ink onto the paper or other object.