What are the differences between wood stain and polyurethane, and which one is more suitable for protecting and enhancing the appearance of wood surfaces?

Wood stain is a coloring agent that penetrates the wood to change its color, while polyurethane is a clear protective coating that sits on top of the wood to provide durability and shine. Polyurethane is more suitable for protecting and enhancing the appearance of wood surfaces because it provides a strong barrier against moisture, scratches, and UV rays.