Nobody knows the difference and no-one can tell you different!!

Nobody = никто = is more often referring to a group. No one = ни один = to define one as much an individual type.

I was taught that the word "one" is a number and "body" is a person. So, when referring to people, use "nobody".

Oh my God! David I'm not ready yet! :) Now it's my turn to scare you with some Russian expressions. ;)

It's interesting that "nobody" would imply a group, when "body" is singular! :) That's English for you! Wait until you learn to use some expressions common to the southern US states, like "y'all" which can be used for an individual OR a group! Y'all take care now! :)