This technique works on the same principle as Hidden Pairs, but is a bit more difficult to apply. The method should be used when we have 3 cells within a column, row, or block that contain notes with three identical digits.
The goal is to exclude notes with other digits and thus "get" the correct values. If you manage to find cells that meet the conditions, then the 3 digits in them can be made the main candidates. The rest of the candidate numbers are discarded.
Let's look at an example of how to use the Hidden Triples technique. In a 3x3 block, the cells are filled with notes with different numbers. We analyze them and see that the same values are repeated in three cells: 2, 3, and 4, while the rest of the cells do not have these values! This means that one of these numbers is definitely in one of the three cells. So these are our "Hidden Threes"! We remove all other notes from these cells, leaving only 2, 3, and 4.
The "Hidden Triples" is a technique that helps you gradually remove "extra values" and get to the point. The "Hidden Triples" method is considered advanced and is used by experienced players to solve hard Sudoku levels.