title: Synchronous and asynchronous callbacks
body: <p>I get confused with some terms while reading MSDN documents and code samples.</p>
  
  <p>What are callbacks in C#? In particular, what are synchronous and asynchronous callbacks ?</p>
  
  <p>Please explain these from a layman's point of view.</p>
  
  <p>Also, please explain the <s>IAsyncCallback</s> <code>IAsyncResult</code> interface.
  How can we implement it? (with very simple example)</p>
  
  <p>Thanks in advance.</p>