What is /Down ?

There are commands like [/Down] and [/Up] I don't know what the difference is between that and [Down] or [/Up]. What does the slash mean?

Means draw a diagonal stroke down or up, like
/
/
/

Analogous to \Down or \Up which I would draw as

\
\
\

I use /up for copy and \down for paste.
/down to close a tab in the browsers and other programs with tabs