user18907: I was playing chess against the computer and captured black’s queen.  All of a sudden, a black pawn appears out of thin air, one space behind the captured queen for a total of nine pawns, and moves multiple squares diagonally.

The computer calls this move “P @ e6,” but after half an hour of scouring the internet, I could not figure out what that means.
1. |  h2 - h4 | Nb8 - c6 |
2. |  e2 - e4 |  e7 - e5 |
3. | Rh1 - h3 | Qd8 × h4 |
4. | Rh3 - h4 |   P @ e2 |

How did this happen?

user8154: You were playing the chess variant called Crazyhouse. In this variant you can place pieces you captured, as one of your color anywhere on the board, instead of a normal move.
I don't know the software you are using, but on Lichess the variant can be selected in the "Create a game" dialog. There should be something similar in your application.


18907: <p>I was playing chess against the computer and captured black’s queen.  All of a sudden, a black pawn appears out of thin air, one space behind the captured queen for a total of nine pawns, and moves multiple squares diagonally.</p>
<p><a href="https://i.stack.imgur.com/Rlflr.png" rel="noreferrer"><img src="https://i.stack.imgur.com/Rlflr.png" alt="board" /></a></p>
<p>The computer calls this move “P @ e6,” but after half an hour of scouring the internet, I could not figure out what that means.</p>
<pre><code>1. |  h2 - h4 | Nb8 - c6 |
2. |  e2 - e4 |  e7 - e5 |
3. | Rh1 - h3 | Qd8 × h4 |
4. | Rh3 - h4 |   P @ e2 |
</code></pre>
<p>How did this happen?</p>
 8154: <p>You were playing the chess variant called <a href="https://en.wikipedia.org/wiki/Crazyhouse" rel="noreferrer">Crazyhouse</a>. In this variant you can place pieces you captured, as one of your color anywhere on the board, instead of a normal move.</p>
<p>I don't know the software you are using, but on Lichess the variant can be selected in the &quot;Create a game&quot; dialog. There should be something similar in your application.</p>
<p><a href="https://i.stack.imgur.com/Ni4M5.png" rel="noreferrer"><img src="https://i.stack.imgur.com/Ni4M5.png" alt="Lichess" /></a></p>
