Particleboard is a manufactured wood product made by pressing together small wood particles, sawdust, and wood chips with glue under high heat and pressure. The result is a flat, smooth panel that looks uniform throughout, unlike solid wood with its natural grain patterns and knots.

Furniture makers use particleboard because it costs less than solid wood and can be produced in large, consistent sheets. Many bookshelves, desk surfaces, and kitchen cabinets contain particleboard covered with a thin layer of wood veneer or plastic laminate to make them look finished. It works well for these purposes, but it's not as strong as solid wood or plywood. If particleboard gets wet, it swells and weakens, which is why you'll rarely see it used outdoors.

The advantage of particleboard is that it uses wood scraps and sawdust that would otherwise go to waste, turning leftovers from sawmills into something useful. The disadvantage is that it's more fragile: screws don't hold as tightly in particleboard as they do in solid wood, and the edges can crumble if handled roughly. When you're assembling furniture from a box, you're often working with particleboard, which explains why the instructions warn you to tighten screws carefully and not overtighten them.