Lumber consists of hardwoods and softwoods. Defined by their pore openings, the hardwoods include cherry, maple, oak, and poplar. Softwoods come from coniferous (or evergreen) trees and range from cedar to pine. Both hardwoods and softwoods receive individualized grades based on their defects.
Outside of these characteristics, lumber also has varying usage characteristics. Rot-resistant, insect-resistant, pressure treated lumber is exclusively for outside usage. Heavier, denser, and stronger than other forms of wood, decking wood includes pressure treated lumber or composite wood, which combines wood with plastic. Used mainly for shelves and sheathing, plywood and oriented strand board come from manufactured wood products, wood byproducts, and glue or resin. General boards come in a variety of sizes and weights to suit various purposes.