container

A container is a lightweight, sealed box that packages your app together with everything it needs to run — the right language version, libraries, settings, all of it. Hand that box to any machine and the app behaves exactly the same, banishing the classic 'but it works on my computer' headache.

Think of it like a shipping container at a port: the crane doesn't care what's inside — a fridge, bananas, car parts — it just lifts a standard box. Your laptop, a teammate's, and the production server all run the same container the same way.

Containers are lighter than full virtual machines because they share the host's operating system instead of bundling their own. Docker is the tool that made them popular, and you'll often hear 'spin up a container' for starting one.