Searching in 2D Grid(c++)

Question

Please take a look: http://www.geeksforgeeks.org/search-a-word-in-a-2d-grid-of-characters/

 

This is a C++ program that searches  a 2D grid for a particular word.

 

In, the code, there are two declarations:  

 

int x[]={-1,-1,-1,0,0,1,1,1};

int y[]={-1,0,1,-1,1,-1,0,1};

 

Can anyone please explain these?? The author says these are for searching in all the 8 directions. But i am not getting how??