HierarchyID datatype in SQL Server 2008

SQL Server 2008 has come up with a NEW datatype, hierarchyID which is system-provided. Use hierarchyid as a data type to create tables with a hierarchical structure, or to reference the hierarchical structure of data in another location.
One needs to deal with Hierarchical data in terms of hierarchical relationships where one data-item is the parent of another data-item.
The most common example where such data exists:

• An organizational structure related application.

SQL server 2008 gives many related hierarchyid functions to query and working with hierarchical data by using Transact-SQL.

If interested in more technical reading, Please refer to below link.
http://www.sqlservercentral.com/articles/SQL+Server+2008/62204/