Docker is an open-source project that provides an operating system-level virtualization environment. It enables developers to package up an application with all of its dependencies into a standardized unit for software development. Docker containers are designed to be lightweight, fast, and portable. Docker containers can be created from any type of application and can run on any type of infrastructure.
It includes everything needed to run an application or service. It runs in its own isolated environment, thereby providing a level of security.