Manhattan distance measures travel along grid lines, not diagonals. The formula is |x₂ - x₁| + |y₂ - y₁|.
If you can only move up, down, left, or right (like in a grid maze), Manhattan distance gives the minimum steps. From (1, 2) to (4, 6), the Manhattan distance is |4-1| + |6-2| = 3 + 4 = 7.
This differs from Euclidean distance (the straight-line formula). Problems involving grid navigation or taxicab geometry use Manhattan distance.