我想用以下类比来说明:

+-----------------------------+-------+-----------+
|             Domain          | Meta  | Concrete  |
+-----------------------------+-------+-----------+
| Docker                      | Image | Container |
| Object oriented programming | Class | Object    |
+-----------------------------+-------+-----------+

I would like to fill the missing part here between docker images and containers. Docker uses a union file system (UFS) for containers, which allows multiple filesystems to be mounted in a hierarchy and to appear as a single filesystem. The filesystem from the image has been mounted as a read-only layer, and any changes to the running container are made to a read-write layer mounted on top of this. Because of this, Docker only has to look at the topmost read-write layer to find the changes made to the running system.

映像的实例称为容器。你有一个图像，它是你描述的一组图层。如果启动这个映像，就有了这个映像的运行容器。同一个映像可以有多个正在运行的容器。

你可以用docker images看到你所有的图像，而你可以用docker ps看到你正在运行的容器(你可以用docker ps -a看到所有的容器)。

因此，映像的运行实例就是一个容器。

Docker映像打包了应用程序运行所需的应用程序和环境，容器是映像的运行实例。

图像是Docker的包装部分，类似于“源代码”或“程序”。容器是Docker的执行部分，类似于“进程”。

在这个问题中，只提到了“程序”部分，这就是图像。Docker的“运行”部分是容器。当容器运行并进行更改时，就好像进程对自己的源代码进行了更改，并将其保存为新的映像。

在编程方面，

图片是源代码。

当编译和构建源代码时，它被称为应用程序。

类似于“当为映像创建实例时”，它被称为“容器”。

虽然将容器看作一个运行的映像是最简单的，但这并不十分准确。

An image is really a template that can be turned into a container. To turn an image into a container, the Docker engine takes the image, adds a read-write filesystem on top and initialises various settings including network ports, container name, ID and resource limits. A running container has a currently executing process, but a container can also be stopped (or exited in Docker's terminology). An exited container is not the same as an image, as it can be restarted and will retain its settings and any filesystem changes.