Here is a game from the 16th Asian Cities Team Championship, GM Ghaem Maghami - IM Eid with full annotations and commentary:
This game was very interesting as it featured two important points where both sides made questionable decisions regarding possible pawn weakening. First white willingly accepted double isolated pawns on c3 and c4. However, these pawns were not easily attacked and turned out to control important squares such as b4 and d4. Then black played the c7-c5 advance which was very committal! This turned out to be a fatal pawn weakening as the d6 pawn was left helplessly backwards. White then easily won this pawn and soon after won the game because of the extra pawn.
This game is a good example of what is a pawn weakening and what is not a pawn weakening. When you are playing your own games you should always ask yourself if a pawn weakening is truly that. Can it be easily attacked? How does the pawn structure difference change the position? What key squares do you now control which you have not before? Can a pawn advance leave another pawn weak and abandoned? These questions can help lead you to make a good decision when choosing how to play the pawn structure in a certain position.