These are the ingredients found in oil-based semitransparents, the most widely used stain type.
Resins and oils carry the pigments and additives into the wood fibers and shield them from water.
Pigments add color to wood and guard it from the sun's ultraviolet rays.
Additives improve finish performance and make the stain easier to apply.
Solvents thin the oils and resins so that they can easily penetrate the wood.