From Sudopedia, the free Sudoku reference guide
Hidden Pair
From Sudopedia
A Hidden Pair is a Hidden Subset of size 2.
When all candidates for 2 digits in a house are limited to only 2 cells, these cells must contain these 2 digits. Subsequently, all remaining candidates can be removed from these 2 cells.
[edit]
Example
The following example shows a Hidden Pair in the second row, for the digits 1 and 7. The red candidates can be eliminated.
