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.
General observations:
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
The major pawn formations:
In his 1995 book, Andrew Soltis classified the major pawn formations into 17 categories, discussed below. In 2015, the book Chess Structures, by Mauricio Flores Rios further studied the subject, subdividing pawn structures into the 28 most important. It is to be noted that for a formation to fall into a particular category, it need not have a pawn position identical to the corresponding diagram, but only close enough that the character of the game and the major themes are unchanged. It is typically the center pawns whose position influences the nature of the game the most
Caro formation:
Openings: Primary: Caro–Kann. Other: French, Scandinavian, QGD.
Character: Slow-paced game.
Themes for White: Outpost on e5, kingside space advantage, d4-d5 break, possibility of queen-side majority in the endgame (typically after the exchange of White's d pawn for Black's c pawn).
Themes for Black: Weakness of the d4 pawn, c6-c5 and e6-e5 breaks. The latter break is usually preferable, but harder for Black to achieve.
we also have the Closed Sicilian formation
in quote i am talking about the chess structure thank you 
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