What does $uid and auth.uid stand for?
<p>Was going through some articles for understanding <strong>Rules &amp; Permissions</strong> in Firebase and then came across conditions like this, for <code>write</code> operation :</p>

<pre><code>{
  "rules": {
    "users": {
      "$uid": {
        ".write": "$uid === auth.uid"
      }
    }
  }
}
</code></pre>

<p>I went with an understanding that <code>$uid</code> stands for Users Push ID and it applies to all dynamic ID's that are generated for <code>Users</code> node.</p>

<p>Then saw this rule else were :</p>

<pre><code>{
  "rules": {
    "articles": {
      "$article": {
        "title": {
                  ".write": "auth != null",
                  ".validate": "newData.isString() &amp;&amp; newData.val() != ''"
        }
      }
    }
  }
}
</code></pre>

<p>If <code>$article</code> stands for Push ID for <code>articles</code> node then Push ID for <code>users</code> node also should have been <code>$user</code>. Isn't it? What is the standard naming convention for declaring Push ID, when configuring rules, so that Firebase parses/understands them correctly. </p>

<p>Lastly, what does <code>auth.uid</code> stands for?</p>