The hurd symlink translator lets you create a filesystem node that
refers to another node.  It is similar to the ln command.  Suppose
you begin writing a new filesystem for the hurd from scratch.  To
develop it quickly, you could skip implementing symlinks.  The user
would instead use the /hurd/symlink translator.  The Hurd could
provide all sorts of filesystem like functionality that would work
regardless of the user's choice of filesystem.
Please note that ext2fs does not use /hurd/symlink.  Instead it
supports linking directly in the filesystem, since that is faster than
using /hurd/symlink.