What is the difference between setContentView and LayoutInflater?

I am creating a tabs list with several fragments. I have noticed that, in the main activity, I used setContentView to get the layout xml and use findViewById to get the corresponding UI element config.

setContentView(R.layout.fragment_tabs);
mTabHost = (TabHost)findViewById(android.R.id.tabhost);
mTabHost.setup();
mTabManager = new TabManager(this, mTabHost, android.R.id.tabcontent);

However, in the different fragment class, I have to use the inflater instead.

View v = inflater.inflate(R.layout.webview, container, false);
WebView myBrowser=(WebView)v.findViewById(R.id.mybrowser);

And both function are used to get the layout xml to create an object, why is there a difference? Is the first one use during onCreate, and the second one during onCreateView? In what situation I should choose either of them?