This technique is similar to Hidden Pairs, but it's a bit more challenging to implement. This method is for when we have three cells in a column, row, or block that contain notes with three identical digits.
The idea is to eliminate any notes with other digits so we can get the right values. If you can find cells that meet the conditions, then the three digits in them can be considered the main candidates. We'll move on and discard the rest of the candidate numbers.
Let's take a 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. When we analyze them, we see that the same values are repeated in three cells: 2, 3, and 4. The rest of the cells don't 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 get rid of all the other notes from these cells, leaving only 2, 3, and 4.
The "Hidden Triples" technique is a great way to gradually remove "extra values" and get to the point. It's considered advanced and is used by experienced players to solve hard Sudoku levels.