A pawn can only move towards the opponent's end of the board. This means that white pawns can only move up the board and black pawns can only move down the board. Pawns cannot move in reverse and they cannot move sideways.
A pawn can move forward one square or two squares on its first move. After its first move it can only move forwards one square at a time.
In diagram 1 the pawn on a2 can move forward one square or two squares. The pawn on g6 can only move forward one square
Diagram 1
Pawn moved 1 square to a3 (diagram 2)
Pawn moved 2 squares to a4 (diagram 3)
Diagram 2
Diagram 3
The pawn on a2 has moved forward to a3 so we simply write a3. In diagram 3 it moves forward 2 squares to a4 we write "a4". We do not put P to indicate that it is a pawn that moves there.
Now let us look at the diagram 1 again and think about the pawn which is on c4. A pawn does not capture an enemy which lies just in front of it so it cannot capture the bishop. A pawn can capture an enemy man which lies diagonally forward. The pawn on c4 can capture either the knight or the rook.
In diagram 4 we see that the pawn has captured. the rook. We write cxb5. This tells us that a pawn on the c file has captured something on c5
Diagram 1
Diagram 4
Look at the first diagram again and think about the pawn on g6. It can move forward 1 square
It has has moved forward to g7, so we write g7. (Diagram 5)
Diagram 1
Diagram 5
On the move after that it can move forward to g8. (Diagram 6)
When a pawn has reached the other side of the board it can be promoted to any piece you want. Usually you will choose the queen because it is the most powerful piece. In diagram below the pawn has been promoted to a queen. You can still promote a pawn to a queen if there is already one queen on the board. (Diagram 7)