Hardwood is derived from deciduous trees (those that lose their leaves) such as oak, maple and birch. Fibers from these trees are short, which add bulk and body to the paper and contribute to the smoothness of the sheet.
Some of the most commonly used softwood trees for paper making include spruce, pine, fir, larch and hemlock. Fibers from these trees are long, which give the paper strength.
Both smoothness and strength are important in the paper making process, so fine papers are made from a mixture of both. Depending on the mill (every mill has their own finely tuned pulp recipe) 85% of the wood pulp used in paper making comes from softwood trees.