title: Command, CommandHandler and CommandInvoker
body: <p>I recently saw a new pattern (new to me) in an open source <code>ASP.NET MVC 3</code> project that hase many <code>Command</code>, <code>CommandHandler</code>, and <code>CommandInvoker</code> -with their interfaces- and I can't understand the pattern! Can you tell me what is this pattern's name and where can I learn about it? And what is its benefits please? Thanks in advance.</p>
  
  <p><strong>Update:</strong> I'm talking about this project:</p>
  
  <p><a href="https://github.com/robashton/RavenGallery/" rel="noreferrer">An image gallery with RavenDB</a></p>