means that on his 45th move, Black captured a piece or pawn on his Queen's Knight Seven square (the b2 square in algebraic notation).
Strategy===== Moves which win material===
There are several basic types of moves that win material.
When a player makes a move which attacks 2 of his opponent's pieces simultaneously with one piece of his own , it is called a '''fork'''. This forces his opponent to essentially, choose which piece he will lose. Knights are especially adept at Forking because their method of movement allows them to attack any other kind of piece without being under attack from that piece. Forks in which the enemy King is one of the pieces under attack are especially effective because they force the opponent to move the king, leaving no choice as to which piece to move. While the knight is the most adept at forking, all of the other pieces are capable of it.
When a player makes a move so that an opponent's piece is in between his attacking piece and another more valuable enemy piece , the move is called a '''"pin"'''. Pinning creates a situation in which the opponent cannot move the piece in question without losing the more valuable piece behind it, effectively "pinning" the piece. A pinned piece can be easily taken.
Skewer is the opposite of the pin. When a player makes a move so that an opponent's valuable piece is directly between his attacking piece and another of the opponents less valuable pieces it is called a skewer. The Skewer forces the opponent to move his more valuable piece out of the way which allows the player to capture the less valuable piece behind it. This especially effective when the King is the skewered piece because the it leaves the opponent with no choice .
Placing both Rooks together
in a rank or file with no pieces in between is a powerful method of attack , because each rook defends the other.
When a player intentionally allows one of his own pieces to be taken in exchange for better position, this is called '''Sacrificing'''. Often, the piece is offered in an attempt to get the players opponent to weaken his own defenses by capturing with a piece that had been in a good defensive position. Morphy was well known for his games featuring many sacrifices, as was [[Mikhail Tal]], a Latvian who was briefly world champion in the 1960s.