Few things about 12 hive folder structure and how well it is mapped with the wsp schema.
SharePoint 2007 have a 12 hive structure which basically contains various files and folders that make SharePoint Interface. The files under 12 hive are mostly Uncustomized, that means they stay on the file system rather than in SharePoint database and perform better while rendering the Pages.
12 hive in SharePoint 2007 has various folders that make up a virtual path for the resources they contain. For e.g to access a CSS file deployed under styles folder we can use a path like
The most commonly used folders are :
\ISAPI\HELP\[LCID] - SharePoint help files. Deploy your own .chm files to this folder (or a localized subfolder)
\CONFIG - Web.config customizations
\ISAPI - SharePoint web services (deploy your custom web services here); this maps to /_vti_bin.
\Resources Global .resx - Files accessed from custom features and site definitions
\TEMPLATE\CONTROLTEMPLATES - deploy .ascx user controls here; maps to /_controltemplates
\TEMPLATE\FEATURES - Features contain folder and related file for each feature.
\TEMPLATE\LAYOUTS - Common site pages; maps to /_layouts
\TEMPLATE\IMAGES - Common site image files; maps to /_layouts/images
\TEMPLATE\SiteTemplates - All SharePoint site definitions; create a \xml to deploy your onet.xml custom site definition
\TEMPLATE\THEMES - All UI elements used in themes; clone an existing theme folder to create your own
\TEMPLATE\[LCID]\XML - Webtemp.xml files to define available site definitions; add an xml file here for your custom site definition
\TEMPLATE\ADMIN Pages - Used by Central Admin; maps to /_admin
\ADMISAPI Administration web services; maps to /_vti_adm
Now lets discuss the most commonly used Folder in SharePoint development.