are the two cells in the same block, row, or column which have exactly the same pair of two candidates and there are no other candidates in these two cells. A picture on the left represents an example of the Naked Pairs
in block (3*2). This is a pair of two numbers '2'
marked yellow in the cells G4 and G6. One of this numbers will occupy the cell G4 and another will occupy cell G6. We cannot tell which number will occupy either of these two cells, but these numbers cannot appear in any other cell of the same block, so we can remove hints '2'
marked red from the cell H6.