<p>These two classes are clearly related. Is <code>SupportFragmentManager</code> used for <code>Fragments</code> generated using <code>FragmentTransaction</code>, while the "regular" <code>FragmentManager</code> is used exclusively to test <code>Fragments</code> generated using <code>.xml</code> files? If not, what is the difference? If so, why are two separate classes necessary to do this? Doesn't that just add extra complexity to the code base?</p>

Difference between Fragment Manager and Support Fragment Manager

These two classes are clearly related. Is SupportFragmentManager used for Fragments generated using FragmentTransaction, while the "regular" FragmentManager is used exclusively to test Fragments generated using .xml files? If not, what is the difference? If so, why are two separate classes necessary to do this? Doesn't that just add extra complexity to the code base?

The concept of Fragments came only after API 11...in order to support those functions in older API version we use Support Libs... I think you have completely mis understood the concept of using support libs.. Do have a look into this question and a quick Google will help u out