Choose the Web application and URL for the Project Web App site. This path is relative to the SharePoint Web Application ...

Choose the Web application and URL for the Project Web App site.

This path is relative to the SharePoint Web Application chosen to host Project Web App. For example, if your Web application is http://site_name, and you want Project Web App to be at http://site_name/projectserver, then the URL path would be projectserver.

To create a Project Web App instance using host header mode, select Use Project Web App path as host header, and enter the full URL that will be used to access Project Server (for example, http://www.contoso.com).