C# => operator?

I have a question about the => operator in C#.

I am looking at the Expression Blend 4 samples. There is one line in the Contact sample which includes:

//In C:\Program Files (x86)\Microsoft Expression\Blend 4\Samples\en\Contacts\
//Contacts\ViewModels\ContactsViewModel.cs: 

contactDetailWindow.Closed += (o, e) =>
{                              
   finishedCallback(contactDetailWindow.DialogResult);

   // Or, C:\Program Files (x86)\Microsoft Expression\Blend 4\Samples\en\
   // Contacts\Contacts\ViewModels\ContactsViewModel.cs
   this.EditContact(newContact, dialogResult =>
   {
        if (dialogResult.HasValue && dialogResult.Value)
        {
        this.Contacts.Add(newContact);
        }
   });
};

What is the => operator actually doing? Is it overriding something?