1. Is it in the Bible?
2. What do we believe it means?
Jesus is Biblically the "Chief Shepherd". he has appointed under-shepherds--pastors--to be His governors over the church.
3. What does it really mean?
This idea is just completely wrong. "Pastoral authority" is a contradiction of Biblical terms. But in our search to verify and uphold the traditional system of operating church we take words and phrases in he Bible--read in our experience--and give them meanings that make us comfortable. I believe the modern term for this is called being a "spin doctor".
So why is jesus referred to here as the "Chief Shepherd"? Well, it has much more to do with his right to be the head of the Church.....
1Ti 6:15 Which in his times he shall shew, who is the blessed and only Potentate, the King of kings, and Lord of lords;
The Word of God is honoring jesus with this title of authority--one which he absolutely deserves.
The question for us is then, do we dishonor Him by pretending that some of us have authority over others within the church?