Please explain why there is an S at the beginning of a filepath?

Please explain why there is an S at the beginning of a filepath?

References

Reference NO 1

http://perldoc.perl.org/File/Path.html

Reference NO 2

http://en.wikipedia.org/wiki/Path_(computing)

Reference NO 3

http://superuser.com/questions/211355/what-does-the-mean-in-a-file-path

Reference NO 4

http://stackoverflow.com/questions/595305/python-path-of-script

Reference NO 5

http://www.cygwin.com/cygwin-ug-net/using.html

Reference NO 6

http://chandoo.org/wp/2012/10/23/extract-file-name-from-full-path-using-formulas/

Reference NO 7

http://php.net/manual/en/function.include.php

Reference NO 8

https://www.graboid.com/support/faq-technical/