Particleboard
Particleboard is an engineered wood product manufactured from wood particles, such as wood chips, sawmill shavings and a synthetic resin or other suitable binder, which is pressed and extruded. Particleboard is a composite material. Particleboard is cheaper, denser and more uniform than conventional wood and plywood and is substituted for them when appearance and strength are less important than cost. However, particleboard can be made more attractive by painting or the use of wood veneers that are glued onto surfaces that will be visible. Though it is denser than conventional wood, it is the lightest and weakest type of fiberboard, except for insulation board.
A major disadvantage of particleboard is that it is very prone to expansion and discoloration due to moisture, particularly when it is not covered with paint or another sealer. Therefore, it is rarely used outdoors or places that have high levels of moisture.
WIKIPEDIA ENTRY FOR PARTICLE BOARD.