1.d4 Nf6 2.c4 g6 3.Nc3 Bg7
In the King's Indian, black permits white to establish a broad pawn center and attempts either to fix that center or to counter-attack it.
Black usually continues with ...d7-d6, ...0-0, ...Nbd7, and ...e7-e5. White will often respond with d4-d5. Black's counter-play will involve f7-f5 and then often with further pawn advances on the kingside with f5-f5 and g6-g5-g4.
In such lines, white will be able to attack on the queenside, hoping to break through and attack the Black king from the back ranks.