French differenatiates between voiced and unvoiced sounds. The sounds concerned are s and sh.
What actually is the difference? The difference is in the use of your vocal chords. They vibrate in the unvoiced version. Actually English has the same. Voiced s are in the words crazy, these. Unvoiced s are in words like sun, fuss, Swiss.
Graphemes for voiced s are: s, z, x, zz
Voiced s
penser (to think)
poser (to put)
embrasser (to kiss)
embraser (to put to blaze)
essentiel (essential)
économiser (to save)
Graphemes for voiced s are: s, ss, c, ç, sc, sth, x