SPACE (Transact-SQL)

integer_expression

Is a positive integer that indicates the number of spaces. If integer_expression is negative, a null string is returned.

For more information, see Expressions (Transact-SQL)

varchar

To include spaces in Unicode data, or to return more than 8000 character spaces, use REPLICATE instead of SPACE.

The following example trims the last names and concatenates a comma, two spaces, and the first names of people listed in the Person table in AdventureWorks2012.

USE AdventureWorks2012;
GO
SELECT RTRIM(LastName) + ',' + SPACE(2) +  LTRIM(FirstName)
FROM Person.Person
ORDER BY LastName, FirstName;
GO

Reference