Sudoku is a logic-based number placement puzzle. The objective of the puzzle is to fill a 9×9 grid so that each rows, columns and 3×3 grids have numbers from 1 to 9. Initially given a partially filled grid you have to use logic to complete the puzzle.
The puzzles owe their popularity in modern times to the ability of software applications to quickly generate puzzles and check the solution for correctness.
I like them because they force you to think and look for all the possibilities.
Currently it is my 9-5 job. I go to office and spend a majority of time solving them on www.websudoku.com