Sql server 2008 user defined data types

Can anybody please tell me what user 开发者_运维百科defined data type is in sql server and also how to create one.

And can i create a user defined datatype which resembles a .net datatable and pass this datatable as parameter to a stored procedure.

See this introductory article here: "What's the Point of [SQL Server] User-Defined Types?"

This answer on SO explains how to pass these UDT types to a stored procedure: Classic ADO.NET - How to Pass UDT To Stored Procedure?