¹Definition: An XYZ-Wing is similar to an XY-Wing, except that the Pivot cell now has all three candidates in it. Also, at least one of the Pincer cells must share the same Block as the Pivot cell. The cell(s) where erasures may take place will also share the same Block with the Pivot cell. This is because the cells that may be erased must overlap the houses of all three cells of the XYZ-Wing.)
Another way to think of it is as an extended Naked Triple where one of the cells lies outside of the Block.

²Look For: A cell with exactly three candidates where there is another cell with exactly two of those candidates in the same Block (Pincer A.) Then look along both of the Pivot cell's Lanes for another instance of a cell with two candidates that match the Pivot (one of which matches the other pincer), this will be Pincer B.

³Consequence: Look along the Lane containing the Pivot and Pincer B, within the Pivot's Block, for the candidate that is common to all three cells (the Pivot, Pincer A, and Pincer B.) These candidates can be erased.

⁴Why it Works: The Z candidate is in all three cells of the XYZ-Wing, so Z cannot exist in any other cell(s) where the three houses of these cells overlap.
It turns out that whatever value (of the three possible) that we try for the Pivot cell, Z appears in one of the three cells:

• If the Pivot is X, then Pincer A is Z.
• If the Pivot is Y, then Pincer B is Z.
• If the Pivot is Z, then the Pivot itself is Z.

Therefore, the Z's on A3 and B3 can be erased.

⁵Now let's take a look at an XYZ-Wing occurring in a real puzzle.

In this example, we have an XYZ-Wing for the candidates 2, 8, and 9.
The Pivot is cell E1, since it has all three candidates.
Pincer A is cell F3, since it shares the same Block as the Pivot.
Pincer B is cell E4, since it shares the same Lane as the Pivot.

⁶The houses of all three cells overlap at E1-E3, and we see that E3 contains a 2: the candidate common to all three XYZ-Wing cells. So, the 2 can be erased from E3 because if E1 turns out to be a 2, then E3 can't be a 2. If E1 turns out to be an 8, then E4 will be a 2 -- so E3 can't be a 2. And, if E1 turns out to be a 9, then F3 will be a 2 -- so E3 can't be a 2.

The Pivot cell is F5. There are two potential Pincer B's, but only one of them results in an erasure; choose that one.