Docker is a computer program that enables users to package applications and their dependencies into a self-contained unit called a container. Containers are isolated from one another and bundle their own software, libraries, and configuration files; they can communicate with each other through well-defined channels. Docker is a platform for developers and sysadmins to build, ship, and run distributed applications, whether on laptops, data center VMs, or the cloud.

Docker is an open-source project that automates the deployment of applications inside software containers. Docker containers wrap a piece of software in a complete filesystem that contains everything needed to run: code, runtime, system tools, system libraries – anything that can be installed on a server. This guarantees that the software will always run the same, regardless of its environment.
How Does Docker Work?
Docker uses a client-server architecture. The Docker client talks to the Docker daemon, which does the heavy lifting of building, running, and distributing your Docker containers. The Docker client and daemon can run on the same system, or you can connect a Docker client to a remote Docker daemon. The Docker client and daemon communicate using a REST API, over UNIX sockets or a network interface.

Docker is built on top of Linux Containers (LXC), an operating system-level virtualization environment that allows multiple isolated Linux systems (containers) to run on a single control host. Docker provides a way to package an application with all its dependencies into a standardized unit, called a container, for software development.
Benefits of Docker
Docker provides several benefits over traditional virtualization technologies:
* Docker containers are lightweight and fast. Containers are much more efficient than virtual machines because they don’t require the overhead of a full operating system.
* Docker containers are portable and can be run on any machine that supports Docker.
* Docker containers are isolated from one another, so there is no risk of applications interfering with each other.
* Docker containers are easy to deploy and scale.
Conclusion
Docker is a powerful tool for developers and sysadmins that enables them to package applications and their dependencies into self-contained units that can be easily deployed and scaled. Docker provides several benefits over traditional virtualization technologies, including portability, efficiency, and isolation. With Docker, developers and sysadmins can quickly and easily deploy and scale applications on any platform.