Nimzowitsch explained this as a protected piece on the opponent’s side of the board that cannot be attacked by a pawn.
Karpov, Anatoly vs Kasparov, Garry 1-0 World Championship 35th-KK5 Rnd:17
Lyon/New York 1990.12.05
ECHESSPEDIA
Quotes of the Day
” (about Lasker) For me, this personality, notwithstanding his fundamentally optimistic attitude, had a tragic note. The enormous mental resilience, without which no chess player can exist, was so much taken up by chess that he could never free his mind of this game, even when he was occupied by philosophical and humanitarian questions.”
Albert Einstein
Carlsen is a combination of Karpov and Fischer style.
Garry Kasparov 2017
I never make mistakes in chess, I only have hallucinations!
Vlastimil Hort 1987
Garry has done a lot over the chess board – unbelievable things. He is the greatest world champion in the chess history. The question is what he has done for the federations, what he has done for his own federation.
Georgios Makropoulos 2013
When your house is on fire, you can’t be bothered with the neighbors. Or, as we say in chess, if your King is under attack, don’t worry about losing a pawn on the queenside.
Garry Kasparov