The aim of the puzzle is to enter the digits 1 through 9 in each cell of a 9x9 grid made up of 3x3 subgrids (called "regions") so that each row, column, and region contains exactly one instance of each digit. A set of clues, or "givens", constrain the puzzle such that there is only one way to correctly fill in the remainder.

Completed sudoku puzzles are a type of Latin square, with the additional constraint on the contents of individual regions. Leonhard Euler is sometimes cited as the source of the puzzle based on his work with Latin squares. -Wikipedia