Why Docker Exists

Without Docker, code that works for one developer breaks for another, in the automated test server (CI — a system that runs and checks your code after every change), and on the server — because every environment differs. In this lesson we see how a single image packages the app and all its dependenc

Docker is like a standard shipping container: pack the app and everything it needs into one box, and every crane, ship, and port handles it the same way.

container: An isolated process created from an image that shares the host kernel instead of booting a full OS.
image: An immutable template (artifact) packaging code, dependencies, and configuration, from which identical containers are created.
host: The machine running Docker Engine that provides containers with CPU, memory, network, and disk.