When building Docker containers you define your base image in your Dockerfile. The scratch image is the smallest possible image for docker. Actually, by itself it is empty (in that it doesn't contain any folders or files) and is the starting point for building out images.
This image is most useful in the context of building base images (such as debian and busybox) or super minimal images (that contain only a single binary and whatever it requires, such as hello-world).
While scratch appears in Docker’s repository on the hub, you can’t pull it, run it, or tag any image with the name scratch. Instead, you can refer to it in your Dockerfile. For example, to create a minimal container using scratch:
FROM scratch
COPY hello /
CMD ["/hello"]
