Why do we need Docker?

 If you have developed an app with a specific version of dependencies that are required to run the app, the same version of dependencies may not have been installed on the other teammates system. This situation might rise a conflict and the app would run on your system but not on the team member's.

To solve issues like this, we use Docker.

Docker is a single unit that contains the application along with all the dependencies. It is a platform that helps us build containers. 

This container can be shared on any OS and the team members donot need to install the dependencies as they are shared through the container.

Container is more like a standardized way to share our application.

Characteristics of a container:

- A container is portable ( can be shared)

- Containers are lightweight (easy to build / update / destroy)

- Containers allow us to build different applications on different versions of the same technology or same dependency.

If we want to build two applications that uses different versions of node, we can create two containers and make it possible.