Some timbers look fine with just a clear oil, varnish, or waxed finish. Others don't - they may have shade variations that need to be evened out, or the wood may not be the colour you want. If you want to enhance or change the colour of, say, a piece of furniture, a door, or floorboards, without obscuring the pattern of the grain, there's a wide range of products to choose from, but there are important differences between stains, dyes, and varnishes.