Ok, I have this question about lyrics, 'cause I think I still don't get something.

What does it mean "who's got my back"? I know what "back" is, but maybe this whole thing means something, that I'm not aware of. How should I understand it. Maybe somehting like and now you see who was right, or who stays behind him,lol... I don't know, that's why I ask. I appreciate any help, thanks in advance.