Naked PairA Naked Pair occurs when exactly two digits are candidates in two cells of a house. You can eliminate these digits from the other cells in this house.
In the sudoku diagram below, in the bottom left box, only the digit 1 and 6 can be placed in the R8C2 and R8C3 cells. Thus, you can eliminate these digits from the other cells of this box. Thanks to this, in the ninth row the digit 6 can only be placed in the R9C9 cell.