Is a 403 error the same as a 401 error? What's the key difference?

No, a 403 Forbidden error is *not* the same as a 401 Unauthorized error. A 401 error means authentication is required – the server doesn't know who you are. A 403 error means the server *knows* who you are, but you don't have permission to access the resource, even after authentication. 401 suggests you need to log in; 403 suggests you're logged in, but still don't have access.