I would love to explain this question as I am part of the team that works with Docker. I'll try my best to explain what Docker is, in the simplest terms.
How was it before Docker?
The developers would build the code and the generated output i.e. artifacts are packaged and available for download and execution. This package would not be independent, if you will try to run it in another platform you will have to install all the needed libraries and functions.
So, what changed after Docker?
With Docker, you can define all the libraries and functions that you require in a docker file. During the build, it will create an image which will push itself to a Docker registry. Now this image is also called as Docker container, as now you can run this application independently anywhere because it has all the dependencies in the container itself.
So, in short, an instance of a Docker image is called a Docker container.
Yes, you can use it in your project. But if your project is very small and if there isn't much configuration or environments to define, you need not to use Docker containers. But if you use so many environments and lot many dependencies to define then it is advised that you use Docker along with Kubernetes. There is also, Microservices that you can use which incorporates, kubernetes and docker.
Tutorial points are the best place to start to learn the basics of any new technologies, once you get a hang of theoretic, you can check with Katacoda.com
Katacoda.com gives you predefined playground which you can use for learning the commands and how to use the latest tool.