A service mesh is a technology that adds reliability, security, and observability features to a platform by creating a dedicated infrastructure layer. It simplifies, secures, and facilitates communication between microservices when dealing with complex, distributed applications at scale. Key components of a service mesh include the data plane (a set of all network proxies that handle and monitor traffic), control plane (centralized component for management processes orchestrating and coordinating the data plane), sidecar proxy (container deployed next to each service in a system handling all its inbound and outbound traffic), and API layer. Some popular service mesh implementations are Istio, Linkerd, Consul Connect, and AWS App Mesh.