Preflight requests?

Short answer: For certain CORS requests (e.g., methods other than GET/POST or custom headers), browsers send an OPTIONS request first, called a preflight. The server must respond with allowed methods, headers, and origins. Properly configured CORS policies handle preflight requests automatically.

Say this in the interview

1. Define — one clear sentence (the short answer above).
2. Example — relate it to a project like ShopNest or your real work.
3. Trade-off — when you would not use it.