Site pages and Application pages

Application Pages:

These pages are normal asp.Net pages and they will reside on the actual file system disk (%ProgramFiles%\Common Files\Microsoft Shared\web server extensions\14\TEMPLATE\LAYOUTS directory) and exist for every site in a Web application.

This folder is mapped to an Internet Information Services (IIS) virtual directory called _layouts. Every site and sub site will have access to the application pages by using the _layouts virtual directory. 

For example, 

http://spdemo2010/_layouts/ viewlsts.aspx and http://spdemo2010subsite/_layouts/settings.aspx access the same application page on the front-end Web server unlike site pages, which are an instance for the specified site.

Site pages:

Site pages can be provisioned to the file system, but their content lives in the content database. Site pages types

·         Standard page –It contains text, images, Web Parts, and other elements.

·         Web Parts page- It contains Web Parts in Web Part zones.

Both types of site pages are edited using a Web browser or Microsoft SharePoint Designer.

Site pages are provisioned from a template page that is stored on the file system of the front-end Web server. When a site is provisioned, SharePoint Foundation creates a pointer to the instance of the page template on the file system. This allows SharePoint Foundation to avoid repeatedly creating copies of the pages, which are provisioned each time a site is created.

Differences between both:

·         Application pages have no content of their own

·         Application pages cannot be edited in Designer or the browser.

·         Application pages are visible under every site in your farm.

·         Application pages are mainly used for configuration pages

·         Both Application and Site pages can use master pages. Application pages get a "dynamicmasterpagefile" property instead of a "masterpagefile" on their @page directive.