Sudoku is a logic-based number puzzle that consists of a 9x9 grid divided into nine smaller 3x3 boxes. The objective is to fill the grid with numbers from 1 to 9, ensuring that each number appears only once in each row, column, and 3x3 box. The puzzle starts with some numbers already filled in, providing clues to help solve it. Players use deductive reasoning to determine the placement of the remaining numbers. Sudoku puzzles vary in difficulty, with easier puzzles having more initial numbers filled in, while harder ones require more complex strategies. It is a popular game that enhances problem-solving skills and concentration.