Istio is an open-source service mesh that enables the connection, monitoring, and security of microservices deployed on-premise, in the cloud, or with orchestration platforms like Kubernetes and Mesos. It provides a layer of abstraction between application code and the underlying infrastructure, allowing for flexibility and scalability. Istio's architecture includes four main components: Envoy sidecar proxies, Mixer policy and telemetry hub, Pilot traffic management, and Citadel security layer. The service mesh provides features such as traffic management, circuit breaking, and load balancing, making it an attractive solution for modern software teams. While still in its infancy, Istio is gaining traction with a growing user base and support from major cloud providers.