There are typically 6 basic levels of sheen to consider when selecting the right paint for any project. An easy way to think of it is, sheen equals shine! The more sheen it has, the more shine it has! And the more shine, the more durability!
Higher sheens are ideal for high traffic areas of your home because of its durability and can be cleaned much easier, while low sheens are better to hide imperfections, they should only be used on lower traffic areas.
The levels of paint sheen are as followed:
Flat / Matte
Flat paint has no gloss and soaks up all the light, ideal to hide imperfections. Not recommended for high traffic areas due to its low durability, and it's nearly impossible to clean.
The next step up from that is Matte finish. Matte finish has very little gloss and reflects very little light. Has great ability to hide flaws while offering a slight shine. Also not recommended for high traffic areas.
Shine: zero-low
Durability: low
Washability: poor
Eggshell
Eggshell is a great middle ground between low and high sheen while maintaining durability. Works great in areas with texture while not reflecting too much light. A subtle shine comparable to the shell of an egg.
Shine: medium
Durability: medium
Washability: good
Satin
Satin finish is a great option for any area of your home. It’s shine offers great durability and is easy to clean. Great for any high traffic area like living rooms, kitchens, bedrooms etc.
Shine: medium
Durability: med-high
Washability: good
Semi-Gloss
Semi-Gloss is a great option for areas with moisture like bathrooms or kitchen. Grease is an easy clean off this finish. An ideal option for trim and baseboards thanks to its incredible durability.
Shine: high
Durability: high
Washability: great
High-Gloss
High-Gloss is exactly what it sounds like, High gloss. This ultra-shiny sheen is extremely durable and super easy to clean. High-Gloss also dries very hard making it a great choice for kitchen cabinets, doors, crown molding, chair rail and other trim pieces throughout your home. One thing to mention is, due to its high reflective properties, it often shows any imperfections or flaws. Best results for this level of gloss is on new areas, or areas in great shape.
Shine: highest
Durability: highest
Washability: best
In my opinion, which is completely subjective, I find that flat and matte work best for ceilings, eggshell and satin work well for walls, and semi-gloss and high-gloss for trim ,baseboards and doors.
Hope this helps clear things up and makes your decision easy when choosing the paint sheen right for your project.