title: Difference between COM DLL and ActiveX control
body: <p>Few similarities I know..</p>
  
  <ul>
  <li><p>Both cannot execute by themself. It needs some program to instantiate it.</p></li>
  <li><p>COM DLL &amp; ActiveX controls are platform independant. (is it so...?)</p></li>
  <li><p>Both requires to support the interface <code>IUnknown</code> and exposes three methods <code>QueryInterface</code>, <code>AddRef</code>, and <code>Release</code>.</p></li>
  <li><p>It also requires to be registered before using and un-registered after done with it.</p></li>
  </ul>
  
  <p>But how are they different? Can someone please list it down?</p>
  
  <p>Also my understanding is ActiveX controls are OLE custom controls (OCX). I have heard of terms like ActiveX DLLs. Is it another form of ActiveX control or something different?</p>