Can someone please explain how the smartphone template works in terms of device detection. I want to maybe see a list of what is smart phones and what is feature phones.

Mobile Joomla only has a template called smartphone (to preview in browser you use device=xhtml)

But what will happen for example when you visit the site from an old phone, like a Samsung E250 ?
It doesn't have its own template assignment, does Mobile Joomla pick this up and also use the smartphone template ? (because that is not a smart phone).