Power Gallery is a solution pack, A solution pack is a prebuilt PHP application. All of the functionality has already been added, you merely need to uplaod the pages to your server and complete the installation
this is different than an Extension. An extension is a tool that is used in Dreamweaver to help you create an application.
Universal Email is an extension that you use to create a PHP application for sending an email.
to find the Poser Gallery Getting Started guide, go to the Power Gallery Support page:
and click on the Getting Started Guide section in the main body.