title: F# type providers, how do they work
body: <p>I don't quite get type providers after watching Don Symes's pdc video
  <a href="http://player.microsoftpdc.com/Session/04092962-4ed1-42c6-be07-203d42115274" rel="noreferrer">http://player.microsoftpdc.com/Session/04092962-4ed1-42c6-be07-203d42115274</a></p>
  
  <p>Do I understand this correctly. You can get ready made type providers for Twitter, Excel...</p>
  
  <p>What if I have a custom Xml structure, do I need to implement my own type provider for that and how is this different from creating my own custom mapper?</p>