The bridge handles the namespacing combinations of JSF in the portal environment. In situations where you need to use the id of an element in your JSF/xhtml markup, you would normally see something like 'form1:myBtn' in the rendered markup. But now with the bridge namespacing you will see something similar to:
Please note that since this uses the portletResponse, once you try to view this page on the servlet application side you will get an exception. To avoid this, you need to check for the type of response in your backing bean and assign a new "safe" namespace variable for the UI.