Sometimes you may want to add a style sheet to only one of your store views, so it affects only this view, and not any other of your views. For instance: you have 2 languages in your site, and for each language you have its own view. One of the languages in your site requires special style rules, for instance – you want to change the directionality to rtl for this language (Hebrew or Arabic). For that you will want to add a special style sheet with some rtl rules.
Here’s something important to know about Magento installation: you should decide in advance whether you want your initial installation to include demo product files, or leave it lean and clean with an empty store.