Revit content is a set of collections of locale- and discipline-specific files to install with your application. This content allows you to work on US or international projects, while referencing appropriate standards for each geographical region.
You can select content on the Select Content page of the installation wizard. There are regions that are grouped by language. When you select a region, it ensures that all of the appropriate libraries and templates are installed.
If multiple regions are selected, you may choose which region to use as a default. Set your region default preference in the Default Content dialog, located below Select Content.
Additional content may be released for Revit products after installation. Click Add Content to browse and select the XML file that contains this content.