Scaffold is a generator to automate the most common tasks in day-to-day of a Front End project. He uses some tools like Yeoman, Grunt e Bower. This generator is all-in-one and have six versions: Mobile, Web, Responsive, Single Page, Single Page Mobile and Single Page Responsive. So you don't need to download each version to scaffolding your project. Just select which version is perfect for you and let the generator do all the stuff. *If you are new to Yeoman, you will find a lot of answers to your questions in their getting started guide.