FROM: The FROM instruction initializes a new build stage and sets the Base Image for subsequent instructions
RUN: The RUN instruction will execute any commands in a new layer on top of the current image and commit the results.
MAINTAINER: The MAINTAINER instruction sets the Author field of the generated images.
EXPOSE: The EXPOSE instruction informs Docker that the container listens on the specified network ports at runtime
ENV: The ENV instruction sets the environment variable to the value
ADD: The ADD instruction copies new files, directories or remote file URLs from and adds them to the filesystem of the image at the path .
ENTRYPOINT: sets PID to 1.
ARG : SET A VARIABLE for DOCKERFILE
WORKDIR : sets working directory
USER : set a container run time user.
VOLUME: creates mount point