Before you start building-out your Magento website you must first plan your store hierarchy.
Magento’s hierarchy is referred to throughout your store’s configuration. Each store can have a separate root category, which makes it possible to run multiple stores, they can be completely independent of each other, or offer alternative channels e.g. Languages, regions.
In addition to your main website, you might have additional websites with a different domain. Within each website, you can have multiple stores, and within each store, separate store views. Many installations have one website and one store, but with multiple store views to support different languages.
A basic website like the green above, may consist of only one website, store and storeview. Or A more complicated set-up might be required for language, currency, audience or catalogue differences like the blue section in the example.
When Magento is installed, a hierarchy that includes a main website, store, and store view is created. You can create additional websites, stores, and store views, as needed.
Setting out your website hierarchy at the beginning will make setting up your catalogue and configuration settings much quicker.