Latex: Aka acrylic or water-based paint (water is the solvent), it's the most DIY-friendly choice because it cleans up with soap and water. Most paint sold today is latex, and in many areas it's the only option available in gallons as more states limit the sale of solvent-based products.
Oil: Known as solvent-based or alkyd paint (mineral spirits are the solvent), it dries slowly and requires paint thinner to clean. But that slow drying time helps oil paint level out, ridding the surface of brush strokes or roller stipples. Oils harden to a durable, enamel shell.
Low-VOC: Paint solvents contain volatile organic compounds that off-gas (creating that paint smell), a health hazard. Recently paint companies have reduced or removed solvents to make healthier products, which are thicker (aka "premium") and dry very quickly. Adding conditioners such as Floetrol or Okon can extend working time without introducing VOCs.
Metal: These paints are formulated to adhere to metal and inhibit rust. Acrylic metal paints are fine for nonferrous metal (such as aluminum), but ferrous metal (like a cast-iron radiator) requires an oil-based metal paint.
Flat or Matte Finish
Paint starts out glossy and loses luster with the addition of titanium dioxide, a chalky material. Flat finishes have the most, making them very low on reflectivity. That means they mask flaws in irregular surfaces, but they scuff easily. The best place for flat paint is on the ceiling, where less reflection is a plus. But mattes can enhance the richness of a deep color when used on a wall.
This finish varies widely by manufacturer. The field is generally a bit more reflective but still nicely balanced and not shiny, as the name suggests. The most popular finish, eggshell is meant for walls that are in pretty good shape. The finish cleans more easily than a flat finish.
A touch shinier, satin finishes make good accents on complex molding profiles or well-prepped window and door casings. They'll resist fingerprints, scuffs, and stains. Satin also works well for kitchens and bathrooms because it cleans well, but it's generally too glossy for other interior spaces.
Shiny without looking wet, this finish can work on any trim. It's better, though, to reserve it for some handsome interior shutters, or allow its superior smudge resistance to protect a banister. All midluster finishes are a matter of taste and circumstance—just prep well, and anything can work.
The shiniest finish available, high-gloss dries to a hard, glasslike sheen. The most brilliant oil-based glosses reflect light almost as well as a mirror, making them great for paneled interior doors or fine furniture, but too shiny for an intricately carved molding or ceiling adornment.