What is a Docker stack?

A Docker stack is correctly defined as a collection of services that make up an application. This encapsulation allows you to manage, deploy, and orchestrate multiple containers that work together as a cohesive unit within a defined environment. Stacks enable developers to define complex applications composed of various microservices, with each service deployed in containers that can communicate with one another.

Utilizing a stack, you can define the necessary environments and interactions through orchestration tools like Docker Swarm, which manages the deployment, scaling, and operation of the services. This allows for effective resource management and simplified configurations, making the development and operation of multi-container applications more standardized and manageable.

On the other hand, a single running container refers only to one instance of a service, which does not encompass the entire application. A type of storage for Docker images is not applicable since a stack does not represent any storage aspect. Lastly, a networking configuration in Docker pertains specifically to how containers communicate within themselves or with other networks, and while networking is a component of containerized applications, it does not define what a Docker stack is.