title: NERDTree toggling and keyboard mapping
body: <p>I have this line in my .vimrc:</p>
  
  <pre><code>nmap &lt;silent&gt; &lt;Leader&gt;p :NERDTreeToggle&lt;CR&gt;
  </code></pre>
  
  <p>So what is the hotkey for toggling NERDTree?</p>
  
  <p>How do I remap it to CTRL-D?</p>
  
  <p>what is the difference between <code>nmap</code>, <code>map</code>, <code>nnoremap</code>, <code>inoremap</code>, etc?</p>