What's the difference between charmeuse vs satin silk?

What's the difference between silk charmeuse and satin silk?

The story starts from yesterday a client from Dubai told me that she wanna charmeuse silk instead of satin silk, and we sold satin silk pillow case to her a few monthes ago, so I asked her the silk charmeuse she want is same like the silk fabrics of silk pillow case she bought? she said, no, it's different, silk charmeuse is more soft. well, before we have a client from U.S, who bought silk charmeuse silk scarf, later we know that the silk charmeuse she said is silk crepe. clearly so many clients confused by the silk charmeuse, as some factories use different name to name same fabrics. so our clients got confused.

So I searched on website, and looked more competitors website, now I could said, silk charmeuse is same as silk satin. some clients use the word charmeuse instead of the word satin because "silk satin" or "silk sateen" has been "hijacked" by polyester manufactureres who use polyester fibers in a satin weave to create the illusion of silk. and you could searched "silk satin" on Alibaba, so many polyester fabrics competitors to use this word to market their products. 

The satin is a kind of fabric weave, like we said silk crepe, silk twill, silk chiffon, etc.. it's also can be made with polyester or viscose, so there's also poly twill, poly crepe, poly chiffon, viscose twill, viscose crepe, viscose chiffon etc..the satin weave has effect of silky surface and a dull back. just like below pictures.

And about the softness of fabrics, it could be adjusted during post-processing, also like sandwashed silk, which is more soft compared with water washed silk satin, or you could call it silk charmeuse.