Dockerfile reference with explanation

Dockerfile

#.dockerignore

#Sets the Base Image for subsequent instructions.
FROM 

#(deprecated - use LABEL instead) Set the Author field of the generated images.
MAINTAINER 

#execute any commands in a new layer on top of the current image and commit the results.
RUN 

#provide defaults for an executing container.
CMD 

#informs Docker that the container listens on the specified network ports at runtime. NOTE: does not actually make ports accessible.
EXPOSE 

#sets environment variable.
ENV 

#copies new files, directories or remote file to container. Invalidates caches. Avoid ADD and use COPY instead.
ADD 

#copies new files or directories to container. Note that this only copies as root, so you have to chown manually regardless of your USER / WORKDIR setting. See https://github.com/moby/moby/issues/30110
COPY 

#configures a container that will run as an executable.
ENTRYPOINT 

#creates a mount point for externally mounted volumes or other containers.
VOLUME 

#sets the user name for following RUN / CMD / ENTRYPOINT commands.
USER 

#sets the working directory.
WORKDIR 

#defines a build-time variable.
ARG 

#adds a trigger instruction when the image is used as the base for another build.
ONBUILD 

#sets the system call signal that will be sent to the container to exit.
STOPSIGNAL 

#apply key/value metadata to your images, containers, or daemons.
LABEL