Docker is an open-source platform that automates the deployment, scaling, and management of applications using containerization. Containers are lightweight, portable, and self-sufficient environments that package an application and its dependencies, including libraries, configurations, and binaries, into a single image. This allows developers to create applications that run consistently across different computing environments, whether on a developer's local machine, in a testing environment, or in production. Docker containers share the host system's operating system kernel, which makes them more efficient and faster to start than traditional virtual machines.

Docker has revolutionized the way software is developed and deployed by enabling continuous integration and continuous deployment (CI/CD) practices, microservices architecture, and DevOps workflows. It simplifies the process of building, testing, and deploying applications, allowing developers to focus on writing code rather than managing infrastructure. Docker also facilitates collaboration between development and operations teams, as applications packaged in Docker containers can be easily shared and deployed across different environments without compatibility issues. The widespread adoption of Docker has made it a standard tool in modern software development, especially for organizations that prioritize agility, scalability, and reliability in their operations.