Schema Files in Sharepoint

Core Schema Files
The following table describes prominent XML files that can be modified for a site definition and shows their locations in the file system.
DOCICON.XML
Maps file ProgIDs and file extensions of document types to specific icons and to controls for opening each type.
\TEMPLATE\XML
WEBTEMP.XML
Specifies configurations for site definitions
\TEMPLATE\1033\XML
ONET.XML
Defines the navigation areas, specifies the list definitions available on the Create Page, specifies document templates and their files, defines the base types for lists, and defines configurations and modules for site definitions.
\TEMPLATE\1033\STS\XML

SCHEMA.XML
Defines the views, forms, toolbar, and special fields in a list definition. Each definition has its own SCHEMA.XML file.
\TEMPLATE\1033\STS\LISTS\List_Definition_Name