PLAY CHESS LIKE A GRANDMASTERLAH

Discovered attack
Garry Kasparov vs. World Team 1999
Kasparov played 12.Nc7+, which forks black's king and rook on a8.
Main article: Discovered attack
A discovered attack is a move which unmasks an attack by another piece. A piece is moved away so as to unmask the attack of a friendly bishop, rook or queen on an enemy piece. If the attacked piece is the king, the situation is referred to as a discovered check. Discovered attacks are powerful as the moving piece may be able to pose a second threat.
A special case of a discovered check is a double check, where the piece being unmasked and the piece being moved attack the enemy king. A double check requires that the opponent moves his/her king as the king is under attack from two directions and it is impossible to counter both at the same time in any other way.
Fork
Main article: Fork
A fork is a move that uses one piece to attack two or more of the opponent's pieces simultaneously, hoping to achieve material advantage, since the opponent can only counter one of the two threats. Knights are often used for forks, with their unique moving and jumping ability. A common situation is a knight jumping to c2 or c7, thereby threatening both the enemy rook and the king. Such "king forks" are particularly effective, because the opponent is forced by the rules of the game to alleviate the threat to the king. The opponent cannot choose to defend the other piece, and thus cannot use a zwischenzug to complicate the situation. Pawns can also be effective for forking. By moving a pawn forward, it may attack two pieces; one diagonally to the left and one diagonally to the right.
Queens are also excellent forking pieces, because they can move in eight different directions. However, this is only useful if both pieces are undefended, or if one is undefended and the other is the opposing king. The queen is the most valuable piece (excluding the king), so it is usually not profitable for it to capture a defended piece.
Pin
Paul Morphy vs. Consultation Team 1858
After Morphy's 14th move, both Black's knight and rook on d7 are pinned.
Main article: Pin
A pin is a move which forces one of the opponent's pieces to stay put because moving it would expose a more valuable piece behind it. Sometimes pinned pieces cannot move at all, as doing so would expose the king. Only bishops, rooks, and queens can pin other pieces, because they move in straight lines.
Skewer
Main article: Skewer
A skewer is a move which attacks two pieces in a line, similar to a pin, except that the enemy piece of greater value is in front of the piece of lesser value. After the more valuable piece moves away, the lesser piece can be captured. Queens, rooks, and bishops can perform the skewer.
Pawns
Pawns are extremely useful in the game and are far more powerful than meets the eye. When a piece cannot be captured without the attacking piece also being captured, pawns will suffice for that purpose. A single pawn approaching will force a more powerful piece, such as a rook or a knight, to retreat. A simple move of a pawn may reveal a hidden threat (see Discovered attacks). Also, when pawns are arranged in a diagonal line, with the frontmost pawns guarded by the pawns behind, they form an almost impenetrable wall capable of protecting any pieces directly behind them. Furthermore, a pawn which has progressed all the way to the opposite side of the board may be promoted to any other piece except a king. However, a weak pawn structure can be a big weakness.
Sacrifices
Colle vs. O'Hanlon 1930
Colle played 12.Bxh7+, an example of the so-called Greek gift sacrifice.
Main article: Sacrifice
Sacrificing some material is often necessary to throw the opponent's position out of balance. The sacrificed material is sometimes able to be regained with interest a couple of moves later. Pawn sacrifices in the opening are known as gambits; they are usually not intended for a short-term gain, but instead to achieve a more active position.
Direct attacks against the enemy king are often started by sacrifices. A common example is sacrificing a bishop on h2 or h7, checking the king, who usually must take the bishop. This allows the queen and knight to develop a fulminate attack.
] Zugzwang
Main article: Zugzwang
Zugzwang (German for compulsion to move) occurs when a player is forced to make an undesirable move. The player is put at a disadvantage because he would prefer to pass and make no move, but a move has to be made, all of which weaken his position. Situations involving zugzwang occur uncommonly, but when they do occur, it is almost always in the endgame, where there are fewer choices of available moves.
Zwischenzug
Main article: Zwischenzug
Zwischenzug (German for intermediate move) is a common tactic which, instead of countering a direct threat, a move is played which poses an even more devastating threat, often an attack against the queen or the king. The opponent has to counter that threat first, and this will ideally change the situation to a disadvantage for that player.
The concept of a zwischenzug is often listed as a tactic, but might properly be called a counter-tactic instead. The effect of a zwischenzug is to change the status quo before a tactic can come to fruition. The near ubiquity of the zwischenzug makes long combinations all the more rare and impressive