What does # mean inside a Dockerfile command?

Question

Docker

The docker documentation https://docs.docker.com/engine/reference/builder/#... has this sentence

"A # marker anywhere else in a line is treated as an argument. This allows statements like:
RUN echo 'we are running some # of cool things'

" this is where i can read about it?

Answer 1

This means that the # symbol will be passed to the command arguments, and not to comment the line.
In the case of this example, the command is echo and the argument is 'we are running some # of cool things'