I don't know who this "G_d" person is either. Do you mean "God"?
You may not be aware of a Jewish tradition of not writing out the full name of God, as a token of respect and awe. That is why you sometimes see the initials "JHWH" to indicate the Hebrew name Yahweh (Whom Christians call Jehovah). Some Christians use the form "G-d" online as a polite courtesy because someone reading their posts may be Jewish, as on this thread; or they may do it from first principles of desiring to honor God in this ancient and harmless way.