It means everything: prior to Paul? There simply **was** no single group calling themselves "christians".The fact that Paul wrote his letters first doesn't mean anything since the Jews of that time depended on oral tradition to communicate. 1 Corinthians 15 demonstrates this fact. Paul uses the language associated with formal transfer of oral tradition.
Likely there was hundreds of individual, small groups--most of whom were still practicing Jews as well.
In fact, there is considerable evidence that the term "christian" did not come into use, until after Constantine's army began force-converting people. They clearly needed a name for the newly-minted cult, so "christian" was used here.
In either case, the oldest stuff (that we have left) comes from Paul-- and Paul (if you remove all the books falsely attributed to him) never wrote about a human Jesus.
Always, Paul writes about a celestial being-- a spirit, a ghost if you will-- never mortal flesh-and-blood.
That is the most telling bit of historical fact right there: the oldest authority we have-- thought Jesus was some sort of mythical figure not unlike Mithras.
The Jesus-as-man comes much later, and appears to be tacked on to the basic Pauline mythos.
And not tacked on very eloquently either...
... which begs the question:
Why is it all such a mish-mash of contradictory information?
If, as they all claim, it's so damnall important?