Modern Algebraic notation:
B=Bishop
N=Knight
R=Rook
K=King
Q=Queen
Pawn moves are indicated by the square they move to, such as "1.e4".
It's a code that weirdos use to communicate with aliens.
Are you crazy maker? It’s actually algebraic notation in chess!
Why for the knight is the letter N ? Why?
You can't use K to represent two different pieces.
The king has been reserved for K, so the knight can no longer use the letter K.
"Knight" sounds like "night", so N is used.