title: channelId, username and tags functionality in API v3
body: <p>I am new in youtube API v3 and I would like to ask some theoretical questions that confuse me a litle. </p>
  
  <ol>
  <li><p>The first question is about the <em>username</em>, <em>chanelID</em> and <em>channelTitle</em>. So far I have understand that in API v3 <em>channelID</em> is the one we should use in order to distinquish users and not <em>usernames</em>. Is that true? If yes this means that each user has a unique channelID by default we he creates an Youtube account? Does the ChannelTitle follows the same logic?</p></li>
  <li><p>The second question I would like to ask is about tags/keyworks that an uploaders optionally attach into their uploads. In the API documentation says that tags are available 
  only for uploaders. This means that we can not retrieve tags for the queried videos through API v3? Until now I could't notice any tag variable into the snippet obtained 
  from <em>video->list</em> for some videos I tested. Is authorization matter? In my account YouTube Analytics API, YouTube Data API v3 are enabled. </p></li>
  </ol>
  
  <p>PS: I am working Youtube API v3 in Python.</p>
  
  <p>Thank you in advance.</p>