title: what's the difference between app-id and app-key on most open platform?
body: <p>In most open platform system, like Facebook, Twitter.</p>
  
  <p>There are three value for client application.
  <strong>App-Id</strong>,<strong>App-Key</strong>,<strong>App-Secret</strong>.</p>
  
  <p><strong>App-Secret</strong> is easy to understand. a secret value never show to public, must not be bundled into client application for security.</p>
  
  <p><strong>App-Id</strong>,<strong>App-Key</strong> both are used to distinguish client application with others. Both maybe bundled into client application.</p>
  
  <p>I think that App-Id/App-Secret pair, or App-Key/App-Secret pair works well for most situation.</p>
  
  <p>Why most platform needs both App-Id and App-Key?
  What's the design purpose?</p>
  
  <p>Now, I think both App-Id and App-Key are just a ID,
  App-Id is a number id, App-Key is a UUID. is it right?</p>