Play with Kubernetes is a labs site provided by Docker and created by Tutorius. Play with Kubernetes is a playground which allows users to run K8s clusters in a matter of seconds. It gives the experience of having a free Alpine Linux Virtual Machine in browser. Under the hood Docker-in-Docker (DinD) is used to give the effect of multiple VMs/PCs. If you want to learn more about Kubernetes, consider the Play with Kubernetes Classroom which provides more directed learning using an integrated Play with Kubernetes commandline.