What is a container?
An app packaged with everything it needs to run: the code, the runtime, the libraries and the settings.
It works on my machine. Every developer has said it. Containers exist so that sentence stops mattering.
What it is
A container packages an app with everything it needs to run: the code, the runtime, the libraries and the settings. It runs the same way on any machine.
How it works
You describe the setup in a file, and build it into an image, a frozen snapshot. Then you start containers from that image, on a laptop, a server or the cloud. Containers share the host's operating system, so they're much lighter and faster to start than full virtual machines. Docker is the best-known tool.
Why it matters
The same image in testing and in production means fewer surprises, and you can run lots of apps side by side without them clashing.
