Play with Kubernetes
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.
https://labs.play-with-k8s.com
Kubernetes for Beginners
In this hands-on workshop, you will learn the basic concepts of Kubernetes. You will do that through interacting with Kubernetes through the command line terminals on the right. Ultimately you will deploy the sample application Dockercoins on both worker nodes.
https://training.play-with-kubernetes.com/kubernetes-workshop/
Katacoda
This is a Kubernetes playground. From here you can play with a Kubernetes host and explore it's API.
Playgrounds give you a configured environment to start playing and exploring using an unstructured learning approach