360-degree appraisal involves obtaining feedback on a manager's performance from subordinates, peers, managers, customers, and suppliers. It aims to provide managers with a more complete assessment of their effectiveness and development needs by reducing bias. The process involves using questionnaires to rate managers on competencies. While it can help with career development and training identification, 360-degree appraisal requires proper implementation to be effective and avoid issues like lack of fair feedback or "ganging up".