Veneer is a thin layer of the real wood on top of a cheaper wood. To disguise it and protect the veneer from peeling, usually there will be an edging of real wood on shelves, etc. and thus a seam that is visible. Good veneer pieces (like parquet or marquetry) use fancy wood (like ebony or burled walnut) that is very rare in an economical and artistic way. Bad veneer is quite visible – often the grain will be going the wrong way – and does not last as well as wood that is a real board, often pulling up or chipping off.
Veneer is always a thin layering of real wood, by the way. If it’s fake wood topping, it should be called laminate.
How Veneer wood is made