A Service Level Agreement (SLA) is a formal document that outlines the expected level of service between a service provider and a client. It specifies the services provided, performance metrics, and responsibilities of both parties. SLAs help ensure that both the provider and the client have a clear understanding of service expectations and accountability. SLAs often include details such as response times, uptime guarantees, and support availability. They are commonly used in various industries, including IT services, telecommunications, and customer support, to maintain quality and foster trust between the service provider and the client.