What does a CORS error mean in FastAPI?

A CORS (Cross-Origin Resource Sharing) error in FastAPI typically means that your web browser is preventing a request from your frontend application (running on one origin, e.g., `http://localhost:3000`) to your FastAPI backend (running on a different origin, e.g., `http://localhost:8000`). This is a security measure implemented by browsers to prevent malicious websites from making unauthorized requests on your behalf.