title: How are android intents handled at runtime?
body: <p>I understand that <code>intents</code> are used to start new <code>activities</code> and <code>services</code> and can contain information about these - certain UI options, etc. They can be emitted by some <code>activities</code> or apps to signal that others should begin or end, or that some change should occur. </p>
  
  <p>I don't understand how these are handled by the System at runtime. Do these go to the OS, where they are relayed to the place where they are needed, or do all <code>Activity</code> instances constantly check every single <code>intent</code> that is  emitted, to see if they apply? </p>
  
  <p>Also, on that note, can all <code>Activity</code> instances "listen" to all intents and if not, how is this "listening privilege" given?</p>