The knight is preparing to go to g3. The option is to take it to d5, but this doesn't seem to be dangerous for Black.
1. e2e4  1... e7e5  2. g1f3  2... b8c6  3. f1b5  3... a7a6  4. b5a4  4... g8f6  5. e1g1  5... f8e7  6. d2d3  6... b7b5  7. a4b3  7... d7d6  8. a2a4  8... c8d7 This is Ding's favorite move in this important position for Ruy Lopez opening theory. 9. b1c3 A move that Carlsen had already tested in the 2010 World Blitz Championship. 9... c6a5  10. b3a2  10... b5b4 