This is considered better than the alternative 8...Ne7.
1. e2e4  1... c7c5  2. g1f3  2... b8c6  3. d2d4  3... c5d4  4. f3d4  4... g8f6  5. b1c3  5... e7e5  6. d4b5  6... d7d6  7. c3d5 Since it was used in some games of the Carlsen-Caruana match, this move has become as important to opening theory as the old main line with 7.Bg5. 7... f6d5 