This method is a good fit when you have two notes with the same number in the same row or column of a 3x3 block. This means that the number is the solution for one of the two cells in this block. That means you can get rid of the number in the other cells in the row or column.
Take a look at the example below for a quick overview. In the top row of the 3x3 block, we see cells with repeating values. We've got 1 and 1, and 9 and 9. There aren't any other repeating numbers in the block, so we can consider these "indicating twos." This means you can get rid of the other 1s and 9s in the row, which we've done in the second screenshot.
The "Pointing Twos" method is one of the more advanced ones and is great for solving not only easy Sudoku, but also medium and hard levels. Once you've got the hang of this method, you can move on to something a bit more complex, like "Pointing Triples."