The Pawn on b4 can capture the black pawn on c5 as it is diagonally next to it. 

The Pawn on b4 can capture the black pawn on c5 as it is diagonally next to it. 

The Pawn:

Pawns are quite unusual because they move and capture in different ways. They move forward, but capture diagonally (sideways) on the chessboard. Pawns can only move forward one square at a time, except for their very first move where they can move forward two squares. Pawns can only capture one square diagonally in front of them. They can never move or capture backwards. If there is another piece directly in front of a pawn he cannot move past or capture that piece.