Voz pasiva y se impersonal
Spanish has TWO main ways to say 'something is done': the classic passive (ser + participle), and the more natural se passive. Plus a special se impersonal for general statements ('Spanish is spoken here').
Voz pasiva — the classic version
ser + participle, with the participle agreeing in gender and number with the subject. La carta fue escrita por Ana (the letter was written by Ana). Los libros son leídos por mucha gente (the books are read by a lot of people). por = 'by'. Common in news and formal text, but rare in everyday speech.
Pasiva refleja with se — much more natural
Way more common in speech: se + verb in 3rd person, agreeing with the noun. Se vende pan (bread is sold) — singular. Se venden libros (books are sold) — plural. Aquí se habla español (Spanish is spoken here). English often translates with the passive, or with 'they / one'.
Se impersonal
Used when there's no specific subject. Se + verb in 3rd person singular + object. Se vive bien aquí (one lives well here). Se come bien en España (the food is good in Spain). No se puede fumar aquí (you can't smoke here). English equivalents: 'one / you (general) / they (general)'.
'Se passive' vs 'se impersonal'
If a NOUN can be the subject — it's pasiva refleja: se venden libros (books are sold). If there's no noun, or it's just a general rule / habit — impersonal: se vive bien (life is good here / one lives well). The line is often blurred in practice.
Estar + participle — state, not action
ser + part. = an action happens/happened. estar + part. = a result / state. La puerta está cerrada = the door is closed (state). La puerta es cerrada cada noche = the door is closed every night (action). English uses 'is closed' for both — Spanish splits them.
Useful templates
Se vende — for sale. Se busca — wanted. Se necesita — needed. Se prohíbe — forbidden. Se ruega — kindly requested (polite signs). Se prohíbe fumar (no smoking). Se busca empleado (employee wanted). You'll see these all over storefronts, doors, and notices.
