title: Why fragments, and when to use fragments instead of activities?
body: <p>In Android API 11+, Google has released a new class called <code>Fragment</code>.</p>
  
  <p>In the videos, Google suggests that whenever possible (<a href="https://www.youtube.com/watch?v=WGIU2JX1U5Y" rel="noreferrer">link1</a>, <a href="https://www.youtube.com/watch?v=sTx-5CGDvM8" rel="noreferrer">link2</a>), we should use fragments instead of activities, but they didn't explain exactly why.</p>
  
  <p>What's the purpose of fragments and some possible uses of them (other than some UI examples that can be easily be achieved by simple views/layouts)?</p>
  
  <p>My question is about fragments:</p>
  
  <ol>
  <li>What are the purposes of using a fragment?</li>
  <li>What are the advantages and disadvantages of using fragments compared to using activities/views/layouts?</li>
  </ol>
  
  <p>Bonus questions:</p>
  
  <ol start="3">
  <li>Can you give some really interesting uses for fragments? Things that Google didn't mention in their videos?</li>
  <li>What's the best way to communicate between fragments and the activities that contain them?</li>
  <li>What are the most important things to remember when you use fragments? Any tips and warnings from your experience?</li>
  </ol>