Using Fragments

I'm a beginner on android. I'm learning using Neri's video lessons, but in his video lessons (android 2.2) I did not use fragments, but in my projects I'm creating it always creates with fragment, so much so that the layout I draw in fragment_main, but I'm not aware use this fragment correctly. Can someone tell me an article that explains this part of the use of fragments, as I'm having problems with it sometimes causing my application to simply close.