user18749: I am a beginner in chess. I am playing a puzzle on chess.com and the puzzle is like this:
White to move
[FEN "r4rk1/p4p2/1p2p2p/2p1P3/3p1q1n/1P1PR1N1/P3QP2/R4K2 w - - 0 2"]

1. Re4

Why is this the best move? Is it purely because this is the only way to save the rook, or this move can even gain some pieces?

user11629: It is the best move because it wins the knight on h4.
Black has only two squares for its queen after 1.Re4:

2....Qf3 3. Rxh4 wins the knight
2....Qg5 3. Rg4 pins and wins the queen

Note that 1. Re4 is not the only move to save the rook. White could also play Nh5 attacking the queen first and if the queen moves save the rook (e.g. via Rg3).

18749: <p>I am a beginner in chess. I am playing a puzzle on chess.com and the puzzle is like this:</p>
<p><strong>White to move</strong></p>
<pre><code>[FEN &quot;r4rk1/p4p2/1p2p2p/2p1P3/3p1q1n/1P1PR1N1/P3QP2/R4K2 w - - 0 2&quot;]

1. Re4
</code></pre>
<p>Why is this the best move? Is it purely because this is the only way to save the rook, or this move can even gain some pieces?</p>
 11629: <p>It is the best move because it wins the knight on h4.</p>
<p>Black has only two squares for its queen after 1.Re4:</p>
<ul>
<li>2....Qf3 3. Rxh4 wins the knight</li>
<li>2....Qg5 3. Rg4 <a href="https://en.wikipedia.org/wiki/Pin_(chess)" rel="nofollow noreferrer">pins</a> and wins the queen</li>
</ul>
<p>Note that 1. Re4 is not the only move to save the rook. White could also play Nh5 attacking the queen first and if the queen moves save the rook (e.g. via Rg3).</p>
