title: What's the difference between an MS Office Visual Studio Add-in, Shared Add-in, and Excel 2010 Add-in?
body: <p>I am using Visual Studio 2010 to create a new add-in for Excel. Ideally I would like it to work with Excel 2011 (Mac), 2010, and 2007.</p>
  
  <p>There are three template options to choose from when I start a new C# project.</p>
  
  <ul>
  <li><p>(Office) Excel 2010 Add-in</p></li>
  <li><p>(Extensibility) Visual Studio Add-in</p></li>
  <li><p>(Extensibility) Shared Add-in</p></li>
  </ul>
  
  <p>What are the differences between these template choices?</p>
  
  <p>Thanks in advance.</p>