They are not really flight modes or features of the drone in the same way that P and ATTI are for example, but rather product certification standards used by different countries to govern things like radio frequencies and to allow the movement of certain products in/through the country. North America uses FCC (Federal Communications Commission) and Europe for example uses CE (Conformité Européenne - or European Conformity). They are just different compliance standards. If you look on the bottom of some of your electronic devices or phone chargers, chances are you'll see a "CE" symbol there.
I see you're in the UK so you may find this to be an informative read:
https://celectronics.com/pdf/ce_brochure_en.pdf