Pawns are The Soul of Chess - Philidor
In chess, the pawn structure (sometimes known as the pawn skeleton) is the configuration of pawns on the chessboard. Since pawns are the least mobile of the chess pieces, the pawn structure is relatively static and thus largely determines the strategic nature of the position.
Weaknesses in the pawn structure, such as isolated, doubled or backward pawns and holes, once created, are usually permanent. Care must therefore be taken to avoid them (but there are exceptions - for instance see Boleslavsky hole below). In the absence of these structural weaknesses, it is not possible to classify a pawn formation as good or bad - much depends on the positions of the pieces. However, the pawn formation does determine the overall strategies of the players to a large extent, even if arising from unrelated openings. Pawn formations symmetrical about a vertical line (such as the e5 Chain and the d5 Chain) can be deceptively similar, but they tend to have entirely different characteristics because of the propensity of the kings to castle on the kingside.
Pawn structures often transpose into one another, such as the Isolani into the Hanging Pawns and vice versa. Such transpositions must be considered carefully and often mark shifts in game strategy