Hi,

Couple of answers:

• files in Resources/LanguageFiles directory are created automatically as part of project creation via VS extensions
• that directory contains Xml files for various localizable resources
• part of the resources are content type property translations
• EPiServer will ask to it's configured collection of localization providers (configurable via web.config file in <episerver.framework> element) specific resources in required language (Admin UI language current user is in)
• and yes - if you add new content type and want to get those page or block properties translated in admin interface - you need to take care of that yourself and add specific resources under correct nodes in Xml file(s)
• [CultureSpecific] attribute just tells EPiServer that concrete property of the content type is editable for all available languages - opposite of "shared property"- that's editable only for master language and read-only for all the other languages

I would recommend to go through globaliazation section in dev guide.

Aaaand of course answer about localization cannot be complete without IMHO a bit nicer alternative - Xml files are pretty clumsy to work with (especially for devs) that's why I created database driven strongly typed localization provider for EPiServer.