Employee retention involves keeping employees within an organization for as long as possible. Key factors that influence an employee's decision to leave include a lack of growth opportunities, poor compensation, and an unhealthy work environment. Effective retention strategies analyze reasons for leaving, focus on compensation, job design, performance management, training, and career development, and aim to make employees feel important, empowered, respected and supported within the organization. Both team leaders and HR departments play important roles in retention by understanding employee needs, providing challenges and career growth, maintaining respect and a healthy work culture, and ensuring proper communication and feedback.