All "dimensions" are stored consecutively in memory.
Consider
int arr[4][100][20];
you can say that arr[1] and arr[2] (of type int[100][20]) are contiguous
or that arr[1][42] and arr[1][43] (of type int[20]) are contiguous
or that arr[1][42][7] and arr[1][42][8] (of type int) are contiguous