How do you play sudoku?

You play sudoku using a set number size such as 4x4. You play sudoku with the numbers 1-4 using a 4x4 puzzle. There are 4 squares in each row and column. Each square must contain one number from 1-4. The numbers cannot be duplicated in the rows or columns but used one time each. Each subsection must also have four numbers ranging from 1-4. Many puzzles start with several numbers filled in. You have to complete the puzzle with the correct placement of the numbers.