comparison of editions – How does the tradition differ between Exalted 2nd and 3rd?

I know the second edition of the legend of Exalted, but I am about to register for a game using the third edition of the legend as a base. (He uses the mechanics of neither one nor the other, but it is not a question of mechanics.)

In order to be more efficient to quickly familiarize ourselves with the world in which we live, I ask:
What are the main differences between the editions?
What are the critical parts to read immediately because the summary of the changes is over-simplification, parts can be caught later, and which parts are largely identical and therefore not worth the time?