Laptop with Windows 10 S?

[Grandmaster Fap!]

Hey folks, apologies if this has been discussed before, my mum is looking for a laptop and ive found some nice deals from a 'high street shop' but one laptop comes with Win10S, doing research seems to suggest you can just turn this off but im confused as to 'S Mode' and just S, they seem to be different versions?

 

[DJ85]

I also wandered this, as I downloaded the drop box app from the windows store and it said "dropbox S"