title: Use case of .Net Bindable Property and Bindable Property Key
body: <p>I'm studying <a href="https://docs.microsoft.com/en-us/xamarin/xamarin-forms/app-fundamentals/custom-renderer/video-player/" rel="nofollow noreferrer">Xamarin Video Player code</a> and got confused by the use of BindableProperty and BindablePropertyKey.  </p>
  
  <p>Under what circumstances/use case do we use BindableProperty over BindablePropertyKey and vice versa. Are they both interchangeable?</p>