Only the third most played move in this position. The original idea of the move 6.h3 is to withdraw the knight to e2 and then play g4-Ng3. Many players also turn the knight back to b3 and then try to play in English Attack style, with Be3 and the g4-g5 push. But the 7.Nf3 move is more difficult to understand, despite having been played in many games. Praggnanandhaa will make his intentions clearer with his next move.
1. e2e4  1... c7c5  2. g1f3  2... d7d6  3. d2d4  3... c5d4  4. f3d4  4... g8f6  5. b1c3  5... a7a6  6. h2h3  6... e7e5 