What is the difference between ENV and ARG in Dockerfile?

In a Dockerfile, ARG and ENV are used for different purposes:

• ARG is a build argument. Its value can be passed during the image build process using docker build --build-arg. Arguments are only available at build time and are not stored in the final image.

• ENV is an environment variable that is stored in the image and available during container runtime.

Example:

ARG VERSION=1.0
ENV APP_VERSION=$VERSION
RUN echo "Building version $APP_VERSION"

Here, VERSION is set during build, and APP_VERSION will be available inside the container after it starts.