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There is a number of opening formations in which one side has a mobile central pawn, eg on e4/e5 or d4/d5, while the other has an extra pawn on the flank. The side with the central pawn strives to organise an advance in the centre, supported by the pawns on neighbouring files, usually the c or f pawn. The opponent attempts to restrict the mobility of the central pawn. Simplification is generally in favour of the player without the central pawn, since he can then exploit his wing majority.

Alexey Suetin, Modern Chess Opening Theory