[2] 3...b6 increases Black's control over the central light squares e4 and d5 by preparing to fianchetto the queen's bishop, with the opening deriving its name from this maneuver.

A rarer third option is 4...Bb4+, which aims to exchange the less useful dark-squared bishop, though this line tends to leave Black with a slightly passive position.

loses material after 6...Bc3 7.Rb1 Bb7 threatening 8...Be4, an opening trap which has ensnared players such as Kamran Shirazi.

Re1 c5 Black has achieved his thematic pawn break before White and the resulting position after 12. e4 dxe4 13.

Ne5 and since Black does not want White to maintain this knight on a strong central outpost, play continues 9... Nfd7 10.

By diverting the black knight on move 9 it is now White who has achieved his central pawn break first.

The effect of Black's check 5...Bb4+ has been to lure White's bishop to c3 where it blocks the c-file.

This, the current main line of the Queen's Indian, is considered equal by theory and became a frequent guest in grandmaster praxis in the 1980s.

More recently, several grandmasters, including Alexander Beliavsky, Ni Hua, Veselin Topalov, and Magnus Carlsen, have played 5.

White has a spatial advantage, but Black has no weaknesses and can choose from a variety of ways to create counterplay, such as 9... c5, 9... f5 or 9... Be4.

These lines are well known for their drawish tendencies and 4... Bb7 is nowadays often employed by Black as a drawing weapon.

Preparing to develop the king's bishop and castle kingside, was also a favorite of Tigran Petrosian.

The Encyclopaedia of Chess Openings classifies the Queen's Indian under codes E12 to E19 according to the following scheme: