What does `docker commit` do, and why is it discouraged for production image builds?

docker commit snapshots a running container's current writable layer into a new image layer, producing a new image. It's useful for quick debugging snapshots, but discouraged for production because it's undocumented and unreproducible — there is no Dockerfile recording how that state was reached, so the build can't be version-controlled, reviewed, or rebuilt deterministically.