What is a multi-stage build in Docker?

A multi-stage build in Docker is primarily defined by its use of multiple FROM statements in a Dockerfile. This allows developers to define different build stages within a single Dockerfile, making it possible to separate the build environment from the final image. By using multiple FROM instructions, each stage can have its own base image and dependencies, ultimately helping to keep the final Docker image smaller by only including necessary runtime files and eliminating any additional artifacts or dependencies that are only needed for building the application.

This approach reduces the size of the final image and enhances security by minimizing the surface area. It also simplifies the Dockerfile by consolidating build steps, which can be beneficial for maintenance and understanding the image's build process. Multi-stage builds are particularly effective in situations where applications require various dependencies or tools only during the build phase, leading to a cleaner, more efficient deployment artifact for production use.