SPWebTemplate.ProvisionAssembly property
SharePoint 2013
Gets the name of an assembly that contains a class that provides logic for provisioning sites created through the site definition configuration or Web template.
Assembly: Microsoft.SharePoint (in Microsoft.SharePoint.dll)
If the SPWebTemplate represents a site definition configuration, this property is the value of the ProvisionAssembly attribute of a Configuration element in a WebTemp*.xml. (See WebTemp.xml for more information.)
The ProvisionAssembly and ProvisionClass properties together identify a class used to support creating sites through the site definition configuration or Web template.