The link above is to a file with a table-valued function called fn_split(). This function allows you to pass a string of values to an IN clause of a SQL query. It breaks them down into a set of rows in a virtual table. Then you use a subquery in the IN clause.
This function is very useful when passing multi-valued parameters in a SQL Server Reporting Services report into a stored procedure. The parameter is defined in the stored procedure as a large varchar string (max 8000 character). In the stored procedure you would reference the function in the WHERE clause where you want to use the multiple parameter values.
WHERE column IN (SELECT [value] FROM dbo.fn_split(@parameter, ','))