List out all INSTRUCTION statement of dockerfile and give one line explanation.

FROM : Set base image

MAINTAINER : Author of docker file

RUN : Run the commands in new layer

VAR : Used to set variable, we can re-use these variables later

EXPOSE : specify port of the container

COPY : Copy files to the container

ADD : copy files into container and extract it

USER : Set the runtime user

ENV : set environment variable

CMD : to set PID1

ENTRY POINT : to set PID1

WORK DIR : set the working directory