Graphic skins
A graphic skin is a 'veneer' which holds the company name, logo and associated page graphics. Changing the graphic design of the whole site generally requires only changing this graphical 'veneer' and requires no changes to site content.
Graphic themes
Graphic themes are based upon Cascading Style Sheets (CSS) which are a simple mechanism for adding style (e.g. fonts, colours, spacing) to Web documents.
The application of graphic themes ensures consistent presentation of content across the site, an important feature when there are multiple content administrators.
Different site areas may also be 'themed' using different style sheets to provide distinctive identities for different departments or services.