Then-last not least-the pawn. It moves one square orthogonally forward, unless he does the first move: then it can move 2 squares, but it`s the only piece that captures different to moving: it captures one square diagonally forward! Pawns can only move and capture forward!But! you can`t move 2 pawns at the beginning at the same time! (As it is often thought), it`s an illegal move!

                   

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 The pawn is the only piece that promotes to a higher piece; but only if it reaches the last opposite rank

Promotion is obligatory, it can promote either to a queen, rook, bishop or knight, but never to a king.