There are three main types of puling processes: Groundwood pulp; Chemical; and Chemi-mechanical.
The groundwood pulping process grinds wood into pulp. Usually this involves taking a log and pressing it against a rotating surface to grind off small pieces. Typically a grinder is about 4 feet long. The groundwood pulp is then often cooked to soften it.
The chemical process involved cooking chips from a log in a hot bath of boiling caustic.
The chemi-mechanical process is a combination of the groundwood and chemical processes.