Nimzo-Indian Defense, Hübner Variation

In the Hübner Variation, Black deliberately gives up the bishop on b4 for the knight on c3. White recaptures with the b-pawn and is left with two pawns on the c-file. In return, White keeps the bishop pair, meaning both bishops, and normally has more central space. The position balances bishops and space against a pawn structure that is easier to attack.

Black commonly advances the c-pawn, develops the knight to c6, captures on c3, and supports the center with d6. Black often adds e5 to close lines and restrict White's bishops, then maneuvers against the pawns on c4 and c3. White tries to open the center so the bishops gain targets.

Doubled pawns are not weak by definition. If they help control the center and White opens diagonals, they can support active play. If they become fixed, Black can attack them repeatedly. The Hübner is a specific branch of the Rubinstein System, not another name for the whole system.