What is a Docker container?

A Docker container is fundamentally a lightweight, standalone executable package that includes everything needed to run a piece of software, including the code, runtime, libraries, and system tools. This self-sufficiency allows applications to run consistently across different computing environments, minimizing compatibility issues that arise from differences in the underlying system configurations. Docker containers share the OS kernel of the host machine while remaining isolated from each other, which is why they are much lighter and faster to start compared to traditional virtual machines that require their own operating systems.

This encapsulation of applications in a single package simplifies dependency management and enables a more efficient use of resources, making deployment and scaling of applications easier in development and production environments. Therefore, the defining characteristic of a Docker container is its ability to package applications and all their dependencies in a way that is portable and efficient.