A theme/template is typically a complete structure and design for a website/webapp/CMS. To elaborate on what Paul said, a skin typically changes the color scheme of a template. A bootstrap package of any sort is typically a completely functional, generic, ready-made package that can be repurposed for many uses--sometimes with a wide array of customization options (and sometimes different skins). A boilerplate package is the stripped-down bare-bones building blocks of something to help get you started. And a framework is essentially just a collection of useful code.