This is what kids call you in online games, especially ROBLOX. You know that it's a kid calling you kid because ROBLOX is a kids game, and no adult with an IQ above room temperature would think calling someone a kid in a kids game is in any way a valid insult.
"Edgy" ROBLOX player: mic up kid you are scared to me ??
Person with a developed brain: Only a kid would call someone a kid in a kids game, kid.
Referring to a friend or another individual. sorta like "what's up bro" but its "what's up kid." Usually used at the beginning and ending of a sentence.