Naked TripleA Naked Triple occurs when exactly three digits are candidates in three cells of a house. You can eliminate these digits from the other cells in this house.
In the sudoku diagram below, in the fifth column in the R1C5, R4C5 and R9C5 cells you can only place the three digits 7, 8 and 9. Therefore, you can eliminate these digits from the remaining cells of this column. Thanks to this, in the middle bottom box the digit 7 can be placed only in the cell R8C4.