What is sudoku?

Answer 1

Sudoku is a puzzle with 9 rows and columns. The rows/columns are divided into 9 3x3 squares (you'll notice the bold lines; those are the things that separate the 3x3 squares.) that are indicated in bold lines. There are many kinds of sudoku. Sudoku was originally called Number Place.

It originated in Japan, hence the name, and was a challenge similar to crossword puzzles, which don't work well with kanji.

Answer 2

Sudoku is a logic-based, combinatorial number-placement puzzle. The objective is to fill a 9×9 grid with digits so that each column, each row, and each of the nine 3×3 sub-grids that compose the grid (also called "boxes", "blocks", "regions", or "sub-squares") contains all of the digits from 1 to 9. The puzzle setter provides a partially completed grid, which typically has a unique solution. Completed puzzles are always a type of Latin square with an additional constraint on the contents of individual regions. (Wikipedia)

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