title: Wordpress: difference between site_id and blog_id?
body: <p>I'm trying to get some understanding of how Wordpress works and while inspecting the database I found that, in a multisite installation, there is a table called <code>wp_site</code> that seems  always holding a single record with a corresponding <code>site_id</code>.
  I cannot understand (nor find on internet) what is the use of <code>site_id</code> when actually multisites seem to use <code>wp_blogs</code> and corresponding <code>blog_id</code> for identifying different sites.(<a href="http://codex.wordpress.org/Database_Description" rel="noreferrer">http://codex.wordpress.org/Database_Description</a>)</p>
  
  <p>Can someone shed some light on what should be my understanding of <code>site_id</code>?</p>
  
  <p>Thanks</p>
  
  <p>Giuseppe</p>