Veneer

Veneer is wood sliced into thin sheets, typically well under 1/16" thick, meant to be glued onto a stable substrate -- plywood, MDF, particleboard -- rather than used as a solid, structural material on its own. Slicing a log this way stretches a small amount of highly figured or expensive wood across far more surface area than the same log could ever cover as solid lumber, which is exactly why rare or dramatically figured species (curly maple, exotic burls) show up constantly as veneer and comparatively rarely as solid boards.

Because the substrate underneath does the structural and stability work, veneered panels also sidestep solid wood's seasonal movement problems almost entirely -- a big advantage for wide panels and tabletops. Slicing methods matter for the resulting look: flat/plain slicing produces cathedral grain similar to plain-sawn lumber; quarter slicing produces straighter grain and ray fleck; rotary-cut peels a continuous sheet off a spinning log, the method behind most utility-grade plywood faces.

That thinness cuts both ways. Sand a veneered panel with anything but a light hand -- especially near an edge, where factory sanding has often already thinned it further -- and it's entirely possible to cut straight through to the substrate underneath, at which point there's no more veneer left to sand with, only a bare patch to explain. Hand-sand veneer, check often, and stop well before you'd stop on solid stock.