Virtual Kubelet is a library and open project that implements the kubelet API without actually running containers on a node. It registers itself with the Kubernetes API server as a Node object, and when the scheduler places a Pod on that “node” the provider implementation translates the Pod spec into something else entirely.
That “something else” is the whole point. Providers have been written for AWS Fargate, Azure Container Instances, Alibaba ECI, HashiCorp Nomad, and AdmiraltyLab’s cross-cluster scheduling, among others. From the cluster’s perspective, Pods come up, report status, and stream logs like any other workload, but underneath they are running on a serverless container service, a separate cluster, or a bespoke runtime. This is the mechanism behind AKS Virtual Nodes and EKS-on-Fargate style integrations.
Virtual Kubelet is a CNCF sandbox project and is primarily a building block: most users encounter it indirectly through a specific cloud provider’s burst-to-serverless feature rather than deploying it by hand.