Introduction Why does “it works on my machine” stop being an excuse the moment a team adopts containers? Because a container ships the machine along with the code. That single shift, packaging an application together with everything it needs to run, is the heart of containerization. A container is an isolated process that carries its own filesystem, libraries, and configuration while sharing the host operating system kernel. The application sees a clean, predictable world. The host sees just another process it can start, stop, and limit.