What are the core components of Docker (images, containers, Dockerfile)?

What are the core components of Docker (images, containers, Dockerfile)?

• A. Containers package software and dependencies; images are templates; Dockerfile defines steps to build an image.
• B. Containers are templates; images build from scripts; Dockerfile defines networks.
• C. Images are running instances; containers are base templates; Dockerfile defines runtime.
• D. Containers are templates; images build from scripts; Dockerfile defines networks.

Answer: (C)

The essential idea is to separate the roles of the three pieces. An image is a reusable, read-only template that contains the filesystem and the instructions needed to reproduce an environment. A container is a running instance of that image, with its own isolated runtime environment. The Dockerfile is a build recipe that specifies the steps to assemble an image—base image, files to add, commands to run, and configuration details—so you can create a new image from those instructions.

So the best way to map them is: images as templates, containers as running instances, and the Dockerfile as the build instructions to create an image. This explains why containers are what you run, derived from the templates, while the Dockerfile is not about runtime but about how to construct the image itself.