user13257: In Sicilian, I see white plays Bc4 after or before I castle.
I saw a lot of players responding to this move by playing e6.
rnbqkb1r/1p2pppp/p2p1n2/8/3NP3/2N5/PPP2PPP/R1BQKB1R w KQkq - 0 1

1. Bc4 e6

In this case people usually respond with e6.
What is good about e6?
Doesn't e6 create a weakness on d6?

user12540: Conceptual Question and almost answered correctly by KMartin . This variation is a favourite of Bobby Fischer and is named as Sozin Variation of Sicilian . The main point in playing e6 is Black protects the f7 square . Let's assume Black plays g6 and then White plays f4 . Black develops the Bishop on g7 . White e5 , de5 fe5 and then Qf3 . So you see that f7 is vulnerable .
One more important function is e6 protects d5 square . Study more Sicilian Schevengien games and you would know it better .

user13055: You have already mentioned one good thing about e6, it blocks the c4-bishop. It may not seem very important, but the white's attack on a2-g8 diagonal can be rather unpleasant later on, especially after white's moves f4 and e5.
Other important factor is the d5 square. Nd5 can be sometimes very unpleasant, so you want to avoid it. It potentially stops even Bd5 (for example after b5).
Black in these structure usually opts for a central break with d5 and e6 supports this plan. That's another reason for playing this move.
We shouldn't also forget the fact that e6 allows to develop the bishop on e7.

To the "weak" pawn on d6:
Here's the deal. You protected c5, d5, e5 and f5, you have avoided some nasty moves like Nd5 or Nf5, you have made some space for your bishop on f8... but there's a price for that. Your d-pawn has become a bit weak.
It's not such a problem, though. Bishop and queen is guarding that pawn and later you can even put a rook on the d-file. Also, as I said, d5 should be coming. That means the weak pawn won't be there forever.

I would say e6 has many more advantages than disadvantages... so I would go for it.

13257: <p>In Sicilian, I see white plays Bc4 after or before I castle.
I saw a lot of players responding to this move by playing e6.</p>

<pre><code>rnbqkb1r/1p2pppp/p2p1n2/8/3NP3/2N5/PPP2PPP/R1BQKB1R w KQkq - 0 1

1. Bc4 e6
</code></pre>

<p>In this case people usually respond with e6.</p>

<p>What is good about e6?<br>
Doesn't e6 create a weakness on d6?</p>
 12540: <p>Conceptual Question and almost answered correctly by KMartin . This variation is a favourite of Bobby Fischer and is named as Sozin Variation of Sicilian . The main point in playing e6 is Black protects the f7 square . Let's assume Black plays g6 and then White plays f4 . Black develops the Bishop on g7 . White e5 , de5 fe5 and then Qf3 . So you see that f7 is vulnerable .</p>

<p>One more important function is e6 protects d5 square . Study more Sicilian Schevengien games and you would know it better .</p>
 13055: <p>You have already mentioned one good thing about <code>e6</code>, it blocks the c4-bishop. It may not seem very important, but the white's attack on <code>a2-g8</code> diagonal can be rather unpleasant later on, especially after white's moves <code>f4</code> and <code>e5</code>.</p>

<p>Other important factor is the <code>d5</code> square. <code>Nd5</code> can be sometimes very unpleasant, so you want to avoid it. It potentially stops even <code>Bd5</code> (for example after b5).</p>

<p>Black in these structure usually opts for a central break with <code>d5</code> and <code>e6</code> supports this plan. That's another reason for playing this move.</p>

<p>We shouldn't also forget the fact that <code>e6</code> allows to develop the bishop on <code>e7</code>.</p>

<hr>

<p>To the "weak" pawn on <code>d6</code>:</p>

<p>Here's the deal. You protected <code>c5</code>, <code>d5</code>, <code>e5</code> and <code>f5</code>, you have avoided some nasty moves like <code>Nd5</code> or <code>Nf5</code>, you have made some space for your bishop on <code>f8</code>... but there's a price for that. Your d-pawn has become a bit weak.</p>

<p>It's not such a problem, though. Bishop and queen is guarding that pawn and later you can even put a rook on the d-file. Also, as I said, <code>d5</code> should be coming. That means the weak pawn won't be there forever.</p>

<hr>

<p>I would say <code>e6</code> has many more advantages than disadvantages... so I would go for it.</p>
