normally hidden directories start with a dot(.) i think that's all

Really so all i need to do is name the folder .pic and no one would be able
to see it?

except if you put in your filemanager "view system and
hidden files" on..
then you also see the hidden directories
else you can change the read permission to your file
to "owner only" but that can give troubles after a
reinstall from a life cd and you change the user name
to something new ...

Put an alias in the system.

alias ls -a='ls'

That way they can use the command.

I think it depends on context. If a person opens Nautilus or whatever
file manager they use in it's default setting, they won't see it. If
they enable 'show hidden folders' or the like, it will be visible.
Likewise, typing 'ls -l' in the terminal will list hidden folders as
well. It depends on the context.

put a "dot" in front of the name.........