What does \??\ mean in \??\C:\Windows\System32\conhost.exe?

I noticed this when trying to find an answer to this question.

It seems to be exclusively associated with conhost.exe only appearing in the command-line parameters for conhost.exe

Also the parameter seems to be the same (on my computer) for all conhost.exe processes:

\??\C:\WINDOWS\system32\conhost.exe 0x4

My question is what does the \??\ signify? Is that some sort of physical device address?The only place I've seen this before is in this image, which came from this article.