title: What does %{ $_.Key1 } mean?
body: <p>While programming for HDInsight I came across lines like</p>
  
  <pre><code>$storageAccountKey = Get-AzureRmStorageAccountKey 
      -ResourceGroupName $resourceGroupName 
      -Name $storageAccountName 
      |  %{ $_.Key1 }
  </code></pre>
  
  <p>I understand <code>$_</code> refers to the result of the <code>Get-AzureRmStorageAccountKey</code> command. But what exactly is the meaning of <code>%{}</code> ?</p>