What is the purpose of a Dockerfile?

A Dockerfile serves as a blueprint for building Docker images. It contains a series of commands and instructions that specifies how to create an image, which includes what software packages to install, what files to copy, and what configurations to set. By utilizing a Dockerfile, developers can automate the image creation process, ensuring consistency and repeatability. This automation is particularly valuable in software development and deployment, as it allows teams to define their application's environment in a code format, which can be version-controlled and reused.

In contrast to the other options, managing Docker containers, creating Docker networks, and monitoring container performance are tasks related to the broader use and orchestration of containers, but they do not involve the creation of images. The Dockerfile's primary role focuses specifically on image construction, making the understanding and use of a Dockerfile foundational for effective containerization practices.