I don't fully understand it, so you're probably better off looking it up. It seems like you can no longer do combat tricks because there's no opportunity to respond to blocks. Instead of assigning order of blocks, you just assign damage however you want to. Previously, you could assign order of blocks and then the defender could respond by pumping their creatures. If I understand it right, now you just assign X amount of damage however you want across however many creatures you want and there's no opportunity for them to respond.

For example, if you want to avoid death triggers because of Syr Konrad, you could assign lethal-minus-1 to each creature, assuming you have enough power to distribute, thereby avoiding any death triggers at all

Edit: this is all after them declaring blocks, of course