New Perspective on Paul?

What is the *New Perspective on Paul*? It's promoted by numerous New Testament scholars such as N.T Wright, James D. G. Dunn and E.P Sanders. I have read a lot of their articles and books on it. I find it really intriguing, and it has shaped my theology. It does kind of challenge the traditional Protestant interpretation of Pauline theology. Although, the scholars I mentioned above themselves are Protestants. What does the New Perspective say that is different?