The whole website and its private area are calculated from templates that are made of static code (mainly HTML) and SPIP elements. These templates are, by default, stored in the squelettes-dist (for the public-facing pages) and prive (for the private area) directories.
For example, when a visitor makes a request for the home page, SPIP creates an HTML page based on the template named sommaire.html. Each type of editorial object in SPIP has a default template that is used to format and display it, such as article.html for articles and rubrique.html for sections (or "rubriques" in French).
SPIP analyses and compiles these templates into PHP code which it stores in a cache. These cached files are then used to produce the HTML pages — which are themselves also cached — and then returned to the site visitor.