Docker is an opensource software using which we can create multiple containers and each container act as an operating system(Not full versioned operating system) in which we can run a particular application.
What is Docker Container?
A container can have a certain quantity of things i.e, A Water bottle can have a certain quantity of water so the water bottle called as container. If you have multiple water bottles and in each bottle you can store different kinds of water (Like, Hot water, cold water and a different flavor of Juices)
Similarly, In your operating system, you can create multiple containers using Docker and you can install your own software application in each container
Example Diagram 1
There are many varieties of products are imported and exported from the countries. Each product different shapes so we can’t put all together in Ship directly. The ships use the big container box and each container contains the products in a proper manner. A Ship contains many containers that hold the Goods. Similarly, we can create multiple containers in our operating system and each container carries a software application. Per Docker Container must have only one software Application on top of the OS in the Docker.
Example Diagram 2
If you understand What is the docker and how the docker looks in our Operating system. Now another question is why we need this? Please watch this full video you will understand the purpose of the docker used for.