Mostly, that I know ~ nothing.
But I think that this was my favorite, and I hope that I am doing Famous Matthew Scholar justice when I quote his ruminations on what we do and don't know about Jesus, after 2000 years of Scriptural writing, commentary, the Jesus Seminar, and whatever:
"I was up in Maine, sitting on the beach one day and looking at a huge barnacle-encrusted rock. And I thought, you know ~ I can't see a single portion of the original rock; it is completely covered in layer upon layer of barnacles. But if you asked me, I could tell you the general shape of the rock."
~ Dr. Dale Allison
He also pointed out in each of the classes I took from him that "Jesus is and does what he says, more consistently and authentically than anyone else. Take a look at the Sermon on the Mount."
I might have learned a few other things. But I think that those are the big ones.