What is a Docker container?
A short, plain-English definition of Docker containers: what they are, why they exist, and how they fit into the way software actually ships today.
Sources
The short version
A Docker container is a lightweight package that holds an application and everything it needs to run, built using operating system-level virtualization [Source 1]. You hand the container to any machine that speaks Docker, and the app runs the same way it ran on your laptop.
That's the whole pitch. The rest is detail.
Where the name comes from
Docker is a set of products that delivers software in packages called containers [Source 1]. The word "container" is doing real work here: think shipping container. Standard shape on the outside, whatever you want on the inside, and the cranes (your servers) don't care what's in it.
Note: Docker the software is unrelated to a "dock" in the GUI sense, like the Windows taskbar that's shipped since Windows 95 [Source 2]. Same English word, different worlds.
What's actually inside a container
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