The Magento theme structure
In Chapter 3, Managing Products, we discussed the Global-Website-Store, or GWS, methodology. As we have learned, Magento allows you to customize many store aspects at some, or all, of the GWS levels.
The same holds true for themes. You can specify the look and feel of your stores at the Global, Website, or Store View levels (themes can be applied for individual Store Views relating to a store) by assigning a specific theme.
In Magento, a group of related themes is referred to as a design package. Design packages contain files that control various functional elements common among the themes within the package. By default, Magento Community installs one design package with two themes.
Themes within a design package contain the various elements that determine the look and feel of the site: layout files, templates, CSS, images, and JavaScript. Each design package must have at least one theme, but can contain other theme variants. You can include any number of theme variants...
