I consider it to be someone who likes Christ or Christianity, as opposed to necessarily being a "Christian". Such a person finds merit, to a greater or lesser amount, in Christianity without identifying him or herself with sanctimonious, so-called "Christians".
I consider it, as opposed to the anti-Christian bigot above me, to be what anyone who's educated would know it to be. The Greek 'phile' means 'lover'. So "Christophile" simply means Christ-lover.
Technically the ignorant individual above makes a point--you can be a Christophile and not be a Christian, or be a Christian and not a Christophile.
Other examples: anglophile, audiophile, bibliophile, logophile, pedophile.