Eggshell: (10 to 25% gloss) Eggshell paints have a slight sheen and reflect a bit more light than a flat finish, but are not highly reflective. They're easier to clean than most flat paints, and slightly more durable, but not as durable as a satin finish or semi-gloss. This is a good choice for walls.
Satin: (25 to 35% gloss) Satins are sometimes lumped in with eggshells, since they also have a light sheen, but they are slightly glossier than an eggshell finish. The subtle reflective qualities give walls a silky finish, adding just enough light to add a slight glow. Since they are durable enough to withstand most dirt and cleaning, they work well in high-traffic rooms (kitchens, bathrooms, kids' rooms, etc.), and can also be used for trim.
Semi-gloss: (35 to 70% gloss) Semi-gloss paints go on smoothly and have a nice gleam without being incredibly shiny. These paints are great for window casings, molding, baseboards, doors, and other trim. They're very easy to clean, and rather durable.
High-Gloss: (70% gloss and higher) High-gloss paints will give your walls a shiny, lacquer-like finish. While these paints can have quite a striking visual effect, they will betray your wall's every imperfection, so properly preparing the walls for a high-gloss job can be arduous. That said, these finishes are very durable, easily cleaned, and make quite a statement.
In conclusion, here are some basic considerations to help you figure out which finish is best for your needs:
• The texture of your walls. The flatter the finish, the less the paint will show imperfections.
• The light and space of the room. Flat finishes can help walls visually recede, and the color can appear deeper because of the low reflectivity. Higher gloss paints will be much more reflective and will help light move around the room.
• What kind of wear, tear, and cleaning the wall will undergo. The higher the sheen, the easier to clean.