What's the main difference between `ARG` and `ENV` instructions in a Dockerfile?

Question

Accepted Answer

`ARG` defines a variable only for the duration of construction, while `ENV` defines a variable that will also be available at runtime.

Answer

`ENV` is only used for network-related environment variables.

Answer

Both `ARG` and `ENV` are used to define persistent environment variables.

Answer

`ARG` is an old instruction replaced by `ENV`.

Question from the Docker test