Sheen describes the degree of light reflection paint has.
Usually the less sheen paint has, the less stain-resistant it is.
Different manufacturers may have various trade names for them, but in general sheens are classified as follows:
Gloss is the toughest.
It cleans easily and resists scuffs better so it's a good choice for areas in constant use, like door jambs and window casings. For shutters and trimwork, gloss paint provides a nice contrast to the siding.
Gloss paint will, however, show imperfections in the surface more than other sheens.
Semi-gloss paints are also durable and easy to clean, but have less shine than gloss.
They are, however, just as suitable for trim work and casings.
Satin (sometimes referred to as eggshell or low luster) offers a good combination of easy-clean and moderate sheen.
It works well on siding that's in good condition.
Flat paint is the best choice for vinyl and aluminum siding that's scratched or dented because it hides imperfections well and spatters less when applied.
It's also easier to touch up.