Roughly, from least to most reflective: flat/matt → eggshell → satin → semi-gloss → gloss.
The trade-off, in one sentence
The flatter the finish, the better it hides imperfections and the worse it cleans. The shinier the finish, the better it cleans and the more it shows every flaw underneath.
Everything else follows from that.
Matt
The default for walls and ceilings, and the right choice for most rooms.
Matt scatters light rather than reflecting it, so undulations, old patches and slightly uneven plaster largely disappear. On older Spanish properties — where walls are rarely perfectly flat — that matters a great deal.
The downside is cleanability. Standard matt marks if you scrub it, and the scrubbed patch ends up shinier than the wall around it.
Use it: bedrooms, living rooms, dining rooms, ceilings everywhere.
Washable / scrubbable matt
A matt appearance with a tougher binder. It cleans far better than standard matt while keeping most of the flaw-hiding.
Costs more. Worth it in any room that gets touched.
Use it: hallways, stairwells, children's rooms, rentals, kitchens if you want a flat look.
Eggshell
A low sheen — noticeably more reflective than matt but well short of shiny.
On woodwork it's the modern standard: durable, wipeable, and far less brittle than traditional gloss, which yellows and cracks in strong sunlight. On walls it gives a subtle depth but starts showing surface flaws, so only over good plaster.
Use it: doors, frames, skirting, architrave. Occasionally walls in bathrooms.
Satin
More sheen again, and correspondingly tougher and easier to wipe.
On woodwork it's a matter of taste — some prefer the slight lift over eggshell. On walls it's useful in wet rooms, but it's unforgiving: every ripple in the plaster catches the light.
Use it: woodwork where you want a bit of shine, bathrooms, utility rooms, kitchen walls.
Gloss
Very durable, very reflective, and very good at showing every imperfection in the surface underneath.
Traditional oil-based gloss also yellows over time — much faster in strong Spanish sunlight — and goes brittle. Most people here have moved to satin or eggshell on woodwork for exactly that reason.
Use it: railings, metalwork, and only where you specifically want the look.
Kitchens and bathrooms
Condensation, steam and cooking residue mean you need something you can wipe. Washable matt or satin emulsion on walls, satin or eggshell on woodwork.
Anti-mould additives are available and genuinely useful in a Spanish bathroom, particularly in apartments where ventilation is limited.
Ceilings
Matt, always. A ceiling catches light across its whole surface at a shallow angle, and any sheen will show every imperfection in it. Ceilings are also almost never as flat as people think.
The practical answer
For most Spanish properties: washable matt on walls, matt on ceilings, satin or eggshell on woodwork. Bathrooms and kitchens get the washable finish; bedrooms and living rooms can have standard matt if you'd rather.