two. a greeting meaning "wusssup?" or "how you doin'?" but in most cases no answer is required.
three. the verbal form of a fist pump.
note: not literally asking about a baby.
"Hey, what's up?"
"No, I think you meant to say, 'how YO baby?'"
George: "How yo baby?"
George: "HEY! It's a form of greeting!"