"Pawns ... are the soul of chess." -- Francois Danican PHILIDOR

"The most important feature of the chess position is the activity of the pieces. This is absolutely fundamental in all phases of the game (opening, middlegame and especially endgame). The primary constraint on a piece's activity is the Pawn structure." -- Michael STEAN

1. The pawn structure is the arrangement of pawns on the board
2. In the endgame, pawns that are isolated, doubled, or backward are weak, and should be avoided
3. The disadavantages of these pawns may be less marked in the middlegame, and there may be compensating advantages
4. If you look at just the pawn structure, you might be able to tell quite a lot about when and where to attack, where you want your pieces, which pieces you want on the board, and so on.
   • For example, the French Defence structure:
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   • White has more space, especially on the King's-side
   • White should avoid exchanges and look to attack on the King's-side
   • White's dark-squared Bishop is their worse Bishop
   • Black has more space on the Queen's-side
   • Black should seek exchanges and look to attack on the Queen's-side
   • Black's light-squared Bishop is quite bad and should be swapped if possible
   • Black's attack on d4 and/or c3 must be hard enough to put White off their attack
   • Black can fight back with ...f6, hoping to exchange or win the cramping Pawn on e5, and fight for space and squares on the King's-side
   • For example, an isolated Queen's pawn position (IQP):
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   • The pawn will always require protection
     • So, at least one White piece will always be tied to defending
     • So, if there are lots of exchanges, that one White piece will be a larger fraction of the White force
     • So, endgames in general will be bad for White
   • The pawn offers a bit more space, more mobility for the White pieces, and an outpost on e5
     • So, with more pieces on the board, especially Queens, White has chances of an attack, against the Black King castled King's-side
5. This sort of analysis can and should be applied to any position, although things are not always so clear
6. You can find more of this sort of thing on the Exeter site: https://exeterchessclub.org.uk/content/pawn-formations