Native XML Webservices introduced by SQL Server 2005, provided a way to access the database engine using SOAP via HTTP. By using this mechanism, we could send SOAP/HTTP requests to the Database Server to execute TSQL Queries, Stored procedures, Functions etc.
This feature will not be available with the future versions of SQL Server. So if you have already used it, make up your mind to modify your applications and avoid using this feature in the future development work. The alternate method being suggested is Windows Communication Foundation (WCF).
You can find the MS article here: http://msdn.microsoft.com/en-us/library/cc280436(SQL.100).aspx