In a microservices architecture, a service mesh manages the communication between microservices. This involves handling service discovery, load balancing, failure recovery, metrics, and monitoring. Service meshes also provide more complex operational requirements like A/B testing, canary releases, rate limiting, access control, and end-to-end authentication. By abstracting these functionalities away from individual microservices, a service mesh allows developers to focus on business logic while ensuring reliable and secure inter-service communication.