Significance of " /proc/<pid>/root"

What is the significance of the directory named root inside /proc/<pid> ? ex: ---------------------------------------------------------------------------------- arunkumar@arun-ThinkPad-Edge-E530:/proc/2543/root$ ls bin cdrom etc initrd.img lib media opt root sbin srv tmp var vmlinuz.old boot dev home initrd.img.old lost+found mnt proc run selinux sys usr vmlinuz ----------------------------------------------------------------------------------