title: What is meant by the 'flex' property of any ExtJS4 layout?
body: <p>I have seen examples where some number is specified against flex, like say</p>
  
  <pre><code>{text: 'Actual', xtype : 'gridcolumn', dataIndex: 'some_data', flex: 1}
  </code></pre>
  
  <p>What is conveyed by this property? The documentation specified is a little difficult to understand, so a simpler explanation would greatly help!  </p>