Template design

Interface is a collection of themes that determines the visual output and frontend functionalities of your store. An interface can be assigned on either the website-level and/or store view-level through the admin panel (Learn how to assign an interface to the website/store).
If you assign an interface in the website-level, all your stores will inherit the interface of your website. You can further assign an interface in the store view-level and store-, effectively overriding that of the website. Say you operate four different stores under a website called “John's Panacea” - By studying the effects of each method as shown below, you can easily determine the method to employ for the design needs of your business.
Website-level declaration
If you want to create a unifying look and feel for all four stores, you will assign an interface in the website level, in which case all four stores will inherit the interface of the website.
Store view-level declaration
If you want to incorporate a separate look and feel per store, you can assign an interface per store-view, in which case the four stores will each carry its own unique look and feel.
Themes
A theme is any combination of layout, osCommerce template, locale and/or skin file(s) that create the visual experience of your store. Magento is built with the capacity to load multiple themes at once, therefore distinguishes themes into two large types: