This is my understanding:
1. Boss
2. Street boss
3. Under boss
4. Consigliere

Note: a acting boss is an unofficial position that serves at the discretion of a boss or family and they can be changed or voted out at anytime, unless, a vote or boss makes them official boss

"McGurn likes you, so I make you. So you are now one of us, if you fuck up, we take it out on McGurn. He is your sponsor. Fuck up, it's his ass. You work in his crew, he is your capo."