I understand the reasoning behind column normalization, as it causes features to be weighted equally, even if they are not measured on the same scale - however, often in the nearest neighbour literature, both columns and rows are normalized. What is the row normalization for/why normalize rows?

I understand the reasoning behind column normalization, as it causes features to be weighted equally, even if they are not measured on the same scale - however, often in the nearest neighbour literature, both columns and rows are normalized. What is the row normalization for/why normalize rows? Specifically, how does the result of the row normalization affect the similarity/distance between row vectors?