I do not know if my wordings in the question is precise enough. There is a specific term for this certain coordinate system which I forgot. I hope that the stack exchange community knows what I am trying to describe.
In said coordinate system, if you are at a point (x,y) then possible movement are only x±1, y±1. In other words, 'left right up down'. If you are to calculate the shortest distance between two points with different x's and y's in said coordinate system, then it would not be a line, it would be step-like.
I have been trying my hardest to find it on google but I didn't find any that matches what I described.