Minor Piece
The Bishops and the Knights are called minor Pieces as compared with the Rooks and the Queen.
Sacrifice
To sacrifice means to give up a man without obtaining for him a man of the opponent or to give up a man for one of lesser value.
Discovered Check and Double Check
A discovered Check is an attack on the King caused by a man moving out of the line of a piece which he was obstructing. If the man discovering the Check also attacks the King the Check is called a double Check.
SYMBOLS FOR MOVES
In addition to the symbols used for squares and men, as explained on page 5, the following are used to indicate the moves:
— means "moves to"
X means "captures"