This is an example starting grid. A standard Sudoku grid is 9*9, you can also get smaller (easier) or bigger (harder) puzzles. Sudoku is a logic puzzle, there is no maths involved, and there is no guessing involved.
There are 3 basic rules to Sudoku puzzles.

1. Every column must contain the numbers 19 once and only once. 
2. Every row must contain the numbers 19 once and only once. 
3. Notice that the grid is seperated in to nine 3*3 boxes drawn in bold. Each of these boxes must contain the numbers 19 once and only once. 