When you are writing T-SQL scripts to save away, for example one to create a new database, there are often optional bits of code you need to run sometimes, and not others.
In the creating a database script, there are quite a few parameters you will want as part of your script. The database name, the settings, whether or not to drop the database or not. Built into SQL Server Management Studio is a cool tool called SQLCMD mode. Scripts using this mode get a few scripting tools that are really useful. These tools allow you to do things like