A backward pawn can be a serious liability. In many games, I avoid the existence or creation of backward pawns at the cost of other positional disadvantages because backward pawns require a lot of support.
When a pawn can no longer be advanced with the support of its neighbors, it is considered backward. Often backward pawn advances are further impeded by opposing pawn placement as well.
Many players become too obsessed with protecting these pawns when they are stuck with them. This is usually a result of a player overvaluing material. In the middlegame, a pawn is not worth very much.
If I arrive at a position in which I have a backward pawn, I will sometimes ignore its existence, and just seek play in another area of the board. I find that this strategy is better than attempting to protect the pawn. If I just defend my pawn, then my opponent's pieces become active and mine passive.
Passive pieces should be avoided at all costs.
White to mate in two moves.