A skewer in chess is an offensive maneuver that targets two pieces in a straight line, much like a pin. However, there is a fundamental distinction between the two tactics. In a skewer, the higher-value piece is directly threatened, whereas the lower-value piece is positioned behind it. Consequently, the opponent is forced to move the more valuable piece to protect it from capture, thereby unveiling the less valuable piece, which can then be seized (referring to the relative value of chess pieces). Skewering is exclusively possible with certain chess pieces, namely bishops, rooks, and queens, whereas kings, knights, and pawns lack this capability.
One encounters two distinct categories of skewers: absolute skewers and relative skewers. It is informative to draw a comparison between these skewer patterns and their counterparts known as pins.
In the context of an absolute skewer, the opposing king is placed in check, necessitating immediate attention to address the check. As a result, the player is compelled to take action, consequently rendering the intended target of the skewer vulnerable to capture or other detrimental consequences.
In the case of a relative skewer, there is no immediate obligation to directly address the pieces involved. However, it is generally considered unfavorable and disadvantageous to neglect addressing the skewered piece.
In the diagram below, White enforced a draw by skewering the black queen. Black is forced to move the queen, then White will capture the black rook, and reach a balanced position.
When contrasting the pin with the skewer in chess, we observe that the pin is a relatively passive maneuver that implies a threat, while the skewer represents a direct assault on the more valuable piece. This distinction makes the skewer a considerably more potent and impactful tactic. In most cases, the target of a skewer finds it difficult to avoid material loss, leaving only the question of which piece will ultimately be sacrificed. Although the skewer is less frequently encountered during actual gameplay compared to the pin, when it does arise, it often becomes a decisive factor in determining the outcome of the game.