How to understand them?

I think it really depends on the context those statements are used in...

But in general, this is what I consider those to mean:


"He is someone" -- He's important, he's not just any random person, he's
different, special

"He is anyone" -- opposite of "someone"; normal, not better, nor worse,
just your average guy, just like any other person

"He is everyone" -- this one is a bit harder to explain without context. It
could mean that he is the only one present. Or I
suppose it could mean that he is does all the work
(he's the writer, the editor, the publisher, etc)


I hope this helps... depending on how you use those, the meanings can change a lot.