Classification of different types of paper based on the type of pulp, treatments, and the end use of the paper is the paper grade.
Although a certain paper grade may be most commonly used for a specific application (such as newsprint for newspapers) it is not necessarily a requirement that you use only that paper grade. You might choose to use cover paper or index paper grade instead of the more common choice of book paper for a brochure, for example. You just need to be aware of the differing characteristics (such as bulk, opacity, or available finishes) that can make certain paper grades more or less suitable for a particular type of document.
Choosing Paper Grade Based on Project has a chart of common desktop publishing print projects and the most common paper grade used for each one.

