When new to the container world, start with Docker first and move on to Kubernetes when you feel ready for it.
For developers:
https://training.play-with-docker.com/#dev
For IT Pros and System Administrators:
https://training.play-with-docker.com/#ops
Containers 101 (even more basic):
https://kube.academy/courses/containers-101
Simple explanation of Kubernetes (8m video):
https://youtu.be/4ht22ReBjno
Kubernetes, getting started with the terminologies and architecture:
https://www.guru99.com/kubernetes-tutorial.html#8
Similar explanation:
https://devetry.com/blog/the-non-technical-guide-to-kubernetes-that%E2%80%99s-admittedly-a-bit-technical/
Kubernetes 101: https://kube.academy/courses/kubernetes-101
Kubernetes Hands-on Workshop
https://training.play-with-kubernetes.com/kubernetes-workshop
Web-based interactive course:
https://www.katacoda.com/courses/kubernetes
YouTube Kubernetes crash course
YouTube playlist: 100 days of Kubernetes covering various concepts and projects
https://youtube.com/playlist?list=PLWnens-FYbIpUpmiiNYfkqTZQUYppGMFV
100 days of Kubernetes in writing: https://devops.anaisurl.com/kubernetes
Articles Kubernetes for Developers:
https://matthewpalmer.net/kubernetes-app-developer/articles/
Kubectl cheatsheet: