Chess Opening Theory/1. d4/1...Nf6/2. c4/2...g6/3. Nf3

=Indian Defence=

3. Nf3
White develops a piece and continues their fight for the central dark squares. This Knight's development, while solid, prevents White's option of playing f3 or f4 and thus gives up options of the aggressive Four Pawns Attack by requiring f4 and the Samisch, which requires f3.

Theory table
.

'''1. d4 Nf6 2. c4 g6 3. Nf3'''