[chongli]

N-KP4 is descriptive notation [1] which was the standard notation used in chess until about 1980. Ne4 is algebraic notation [2] which is the standard notation used in chess today (since 1980).

[1] https://en.wikipedia.org/wiki/Descriptive_notation

[2] https://en.wikipedia.org/wiki/Algebraic_notation_(chess)

[jessaustin]

I'm relieved to see that the following is included at that link:

The term "algebraic notation" may be considered a misnomer, as the system is unrelated to algebra.