I am trying to give you a very simple explanation which will clear your doubts regarding these things.
Containers: Talking about containers, so it is your box. Pack books, pack machines in it totally your choice. To the outside world it's just a container, to you and your partners it's the box of stuff to make magic happen.
Docker: On the other hand docker is the company logo on the container box. Each container is manufactured differently, by the manufacturer, but they all serve one basic purpose, SHIPPING YOUR CODE.
Kubernetes: At last talking about Kubernetes, so it is the shipping company/ yard which manages these containers at various locations i.e environments, read Dev Qa Prod etc.
In order to learn all these technologies, I would suggest you must take up the following DevOps training Course. If you like reading things then you can read the following DevOps tutorial. I am also mentioning a video tutorial of DevOps which you can refer to learn more about these technologies. .