A Service Mesh is a dedicated infrastructure layer that manages communication between microservices in a cloud-native application. It provides features like load balancing, service discovery, and security, allowing developers to focus on building applications without worrying about the complexities of service interactions. By using a Service Mesh, organizations can enhance observability and reliability in their systems. It typically employs a sidecar proxy pattern, where a lightweight proxy is deployed alongside each service instance, handling all network traffic and enabling features like monitoring and policy enforcement without modifying the application code.