title: What's the difference between the build and create methods in FactoryGirl?
body: <p><a href="https://github.com/thoughtbot/factory_girl/blob/master/GETTING_STARTED.md">The Factory Girl introduction</a> delineates the difference between <code>FactoryGirl.build()</code> and <code>FactoryGirl.create()</code>:</p>
  
  <pre><code># Returns a User instance that's not saved
  user = FactoryGirl.build(:user)
  
  # Returns a saved User instance
  user = FactoryGirl.create(:user)
  </code></pre>
  
  <p>I still doesn't understand the practical differences between the two. Can someone give an example where you would want to use one and not the other? Thanks!</p>