Sheens

Sheen decides durability and how much the surface hides. It is a trade-off, not a quality ladder: the more sheen, the more washable, and the more every flaw shows.

Sheen	Where it goes	Why
Flat / matte	Ceilings, low-traffic walls, and any surface with visible imperfections.	Scatters light, so it hides roller marks, patches and wavy drywall better than any other sheen. The trade-off is washability: scrubbing a flat wall burnishes it and leaves a shiny patch.
Eggshell	Living rooms, dining rooms, bedrooms and hallways.	The default interior wall sheen in most of the US. Enough sheen to wipe, little enough to keep hiding minor surface flaws.
Satin	Kitchens, bathrooms, kids' rooms and laundry rooms.	More washable than eggshell and more forgiving than semi-gloss. Shows application marks if you break the wet edge, so keep moving.
Semi-gloss	Trim, doors, cabinets and bathroom walls.	Hard, washable and moisture-tolerant. The standard trim sheen. It reveals surface preparation, so sanding and filling matter more here.
Gloss	Front doors, furniture, accent trim and high-wear surfaces.	Maximum durability and the easiest to clean. It also shows every flaw in the substrate — a gloss finish is a decision to do the prep properly.