Use ser for what something is or where it is located: jobs, origin, qualities, and the place a thing stands. Use estar for temporary conditions and how someone feels or is doing.
Examples
- Sóc enginyera i treballo en una empresa petita.
- I'm an engineer and I work at a small company.
- L'oficina és al centre, a prop de l'estació.
- The office is in the centre, near the station.
- Avui estic cansat, he tingut molta feina.
- Today I'm tired, I've had a lot of work.
- Estem contents amb els resultats.
- We're happy with the results.
The mistake to avoid
Unlike Spanish, Catalan uses ser for where things are: L'oficina és al centre, not *està al centre*.
Where this fits in
Feina i estudis, Catalan B1: Talk about your job, workplace, and studies; give reasons and opinions.