What is meant by "container image"?

A "container image" refers to a snapshot of a filesystem and parameters that define the software environment for a Docker container. This image serves as a blueprint for creating Docker containers, encapsulating everything needed to run an application, including libraries, binaries, and configuration files. When a container is instantiated from this image, it operates in a lightweight, isolated environment, which ensures that the application runs consistently across different environments.

The concept of a container image allows developers to package applications and their dependencies into a self-sufficient unit, making deployment and scaling significantly easier. By using a layered filesystem, images allow for efficient storage and sharing, where only changes between layers need to be stored if a new image is created based on an existing one.

The other options do not accurately describe what a container image is. A compressed archive of Docker containers refers to a different format and stage in Docker workflow. A running instance of a Docker application describes a container, not the image itself. A log of Docker container events pertains to monitoring and tracking activity rather than defining the structure or purpose of an image. Hence, the definition as a snapshot of a filesystem and parameters is the most accurate description of a container image.