Just as rooks become more powerful on open files and the value of the knight increases towards the center, so too the pawn becomes more powerful and more threatening as it nears the queening square on the final rank. You will often find that your opponent will have to give up a knight, a bishop, or sometimes more in order to prevent a pawn from reaching the queening square.
In the following diagram, the white pawn on e6 is a very powerful weapon in no small part because white has placed a queen to help guide in the pawn. After white pushes the pawn, black must give up the knight immediately or else a rook when the pawn reaches the e8-queening square.