title: What's the difference `{'x'=> 3}` and `{x: 3}`?
body: <p>I have this:</p>
  
  <pre><code>a = {'x' =&gt; 3}
  b = {'x': 3}
  c = {x: 3}
  d = {:x =&gt; 3}
  e = {:'x' =&gt; 3}
  </code></pre>
  
  <p>So, I have that <code>b = c = d = e = {:x =&gt; 3}</code>, meanwhile <code>a = {"x" =&gt; 3}</code> but <code>a.class == b.class</code>.</p>
  
  <p>I don't understand what the difference is between <code>a</code> and the rest of variables.</p>