Mirrored from Sudopedia, the Free Sudoku Reference Guide
A Naked Triple is a Naked Subset of size 3.
It is formed by 3 cells that have candidates for only 3 digits and are collocated in the same house.
In this example, observe that r1c3, r2c3 and r5c3 contain ONLY candidates that are a subset of the digits 6, 7 and 8, and these three cells are all collocated in column 3. As such, these three digits must go to these three cells, so 6, 7 and 8 can be eliminated from all other cells in column 3. In this example, column 3 is the house.