Core (Plywood Core)

The core is the interior structure of a plywood panel, sandwiched between its outer face veneers -- and it varies more between plywood products than almost anything else about the sheet. Veneer core stacks alternating layers of solid wood veneer with the grain direction rotated 90 degrees between layers, the traditional and generally strongest, most stable construction. MDF core and particleboard core substitute a solid, uniform manufactured panel for the inner veneer layers -- flatter and heavier, with better screw-holding in the face but worse holding at the edges than veneer core.

Core construction is worth checking before buying, not just face veneer species -- two sheets of "birch plywood" can behave very differently in weight, screw-holding, and edge strength depending on what's actually sandwiched inside.