Kraft paper is strong, relatively coarse paper produced by the kraft process from wood pulp. It is used, amongst other things, in grocery bag and envelope packaging. It is a robust paper suitable for a variety of packaging uses, including wrapping books and thick documents.
The Kraft process is a type of wood pulping process which leads to stronger fibres than more acidic pulping. Its strength makes it a suitable packaging material. Kraft pulping produces a dark pulp - hence its brown colour. But the pulp can also also be bleached to form a very white pulp for high quality paper.