title: Difference between ItemsSource and DataContext as pertains to ListBox
body: <p>I am not quite grokking the difference between ItemsSource and DataContext.  Can someone explain it and back it up with examples?  When would I use one or the other.</p>
  
  <p>I am reading the docs and it says that I can bind using DataContext, but I throw an ObservableCollection at it and nothing shows up in the list.  If I throw the same collection at the ItemsSource, it works fine.</p>