What's the difference between real dual-touch and fake dual-touch?

I have a Xperia X10 Mini Pro and by some ungodly reason it's dual touch feature is not working. I have searched around the net and I have seen here and there people use terms such as real dual-touch and fake dual-touch. I don't really understand what's the difference here? Can the dual-touch ability be faked and how is that possible? By the way, if anyone can tell is it possible to activate the dual touch feature in my phone I would be super thankful.