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Docker is a piece of open-source software that is intended to help and simplify application development. It is a collection of platform-as-a-service solutions that provide separated virtualized environments for developing, deploying, and testing applications.

Although the program is reasonably straightforward to use, certain Docker-specific jargon may be unfamiliar to novice users. Dockerfiles, images, containers, volumes, and other jargon must be learned and should become second nature over time. One of the most common queries from users is: What exactly is the difference between a Docker image and a container?

Read on to learn.

What is a Docker Image, and how does it work?

A Docker image is an immutable (unchangeable) file that includes all of an application's source code, libraries, dependencies, tools, and other files.

The notion of an image and a container is similar to that of a class and an object, where the object is an instance of the class and the class is the blueprint for the object. Virtual Machines and Docker images are not the same things; virtual machine images are simply snapshots of a running virtual machine at various points in time, whereas Docker images are slightly different, and the most important and significant difference is that Docker images are immutable, meaning they cannot be changed.

In the real world, it is common for a program to run on one computer but not on others owing to differences in surroundings. This problem is totally handled by Docker images, which allow an application to operate on any PC. Every developer in a team will be working in the same development environment. Each testing instance is identical to its development counterpart. Your production and testing instances are identical. Developers from all around the world may also share their Docker images on the Docker HUB platform.

These photos are commonly referred to as snapshots because of their read-only status. They represent a single instance of a program and its virtual environment. One of Docker's best advantages is its constancy. It lets programmers test and experiment with software in a controlled, consistent environment.

You can't start or execute pictures since they essentially simply template. You may design a container using that template as a foundation. In the end, a container is nothing more than a running image. When you create a container, it adds a readable layer to the immutable image, allowing you to edit it.

The image base from which you build a container lives independently and cannot be changed. When you operate a containerized environment, you're effectively creating a read-write duplicate of the filesystem (docker image) within the container. This creates a container layer that enables you to edit the full picture copy.

From a single image basis, you can create an infinite number of Docker images. You build a new template with an extra layer on top of an image every time you alter the initial state and save the current state.

As a result, Docker images may be composed of a number of layers, each of which differs but is related to the one before it. When you use it to set up a virtual environment, image layers represent read-only files to which a container layer is appended.

What is a Docker Container, and how does it work?

Users may separate programs from the underlying system using Docker containers, which are virtualized run-time environments. These containers are small, portable components that allow you to rapidly and simply establish an application.

The uniformity of the computing environment operating within the container is a useful feature. It not only ensures that your application runs, in the same way, every time, but it also makes sharing with other coworkers a breeze.

Containers offer robust isolation since they are self-contained, guaranteeing that they do not disrupt other containers or the server that runs them. These units, according to Docker, "offer the greatest isolation capabilities in the industry." As a result, you won't have to be concerned about keeping your computer safe when building an app.

Containers virtualize at the app layer, unlike virtual machines (VMs), which virtualize at the hardware level. They can execute separate processes on a single computer with a shared kernel and virtualized operating system. As a result, containers are incredibly light, enabling you to save critical resources.

If a Docker image is a house map, then a Docker Container is the actually built home, or in other words, an instance of the image. Containers are runnable instances of an image, according to the official website. Using the Docker API or CLI, you may create, start, stop, move, or destroy a container. You may attach storage to a container, link it to one or more networks, or even construct a new image based on its existing state.

A cluster of containers runs an application, which is self-isolated from one another and from the host machine on which they are running. For example, if a backend application is running on a docker container at port 8000 and you try to access it from the host machine, you will be unable to do so because containers are self-isolated. In this case, you must explicitly expose your application at a specific port and connect your machine port to that port.

Docker image	Docker container
It's the Container Blueprint.	It is an Image instance.
A logical entity is an image.	A container is a real-life object.
The image is only made once.	Images may be used to form containers in any number of ways.
Images are unchangeable.	Containers only change if the old image is removed and a new one is utilized to construct the container.
Working with 5 Images does not need the use of any computational resources.	Containers, like Docker Virtual Machines, need computer resources to execute.
You must develop a Dockerfile script to create a docker image.	To create a container from an image, use the "docker build." command.
Docker Image does not have a running state.	Containers utilize RAM when they are built and while they are operating.

Conclusion

Once you've figured out how to make a container, you'll be able to tell the difference between pictures and containers with ease. You should now have a clear understanding of what a Docker image is, what a container is, and how they are related after reading this article. Stay tuned to more articles on Docker.