Sudoku Rules: How to play Sudoku

What is the overall goal of Sudoku?

Sudoku is a puzzle game using numbers that can be solved entirely with numbers 1 to 9 and logic. It is important to remember that since these are logical puzzles, no guessing is allowed to find which number should be assigned to a cell. Well designed Sudoku puzzles only have one unique solution.

What are the rules of Sudoku?