You know what is a backward pawn? It is a pawn standing behind his neighbour pawn, but without defending support by other pawns
Here in this example d6 is such a backward pawn. Putting a white pawn on e4 you may understand that it could become a weakness
A.Strategy playing against the backward pawn
One main strategy is to blockade and attack that pawn, f.e by his heavy pieces
As you see the weak backward pawn can often be defended , but the pieces are bound. So a typical method is to create a second weakness elsewhere - and win!
Another white strategy is to reach an endgame with Knight/dark-coloured Bishop
Obviously White has the better endgame. So let´s see how the both strategies can work in practise.