Why source property need not be a dependency property in data binding in WPF?

Question

Hi,

    I am very much confused with one fact in WPF Data Binding. WPF says that in data binding, where we bind source property to some target property, target property should be dependency property but source property need not be dependency property. But it appears reverse to me, reason being as follows.

   Binding means that when ever the value of source changes than target value should be updated.

Now I ahve 2 questions
1. If the source property is not a dependency property than how does change notification goes from source property to target property.
2. I dont understand the need for target to be dependency property in binding?

I think I am definitely missing something here. Can someone please clear my confusion?


Thanks,
shaba.