Along with the static text, code and comments, you can also use the predefined variables (listed below) that will be then expanded like macros into the corresponding values.
Using the #parse directive, you can include templates from the Includes tab, by specifying the full name of the desired template as a parameter in quotation marks.
It is also possible to specify arbitrary number of custom variables in format ${<VARIABLE_NAME>}. In this case, before creating a new file/class/interface IDEA will prompt you with the dialog where you can define particular names for all custom variables.
Predefined variables will take the following values:
${PACKAGE_NAME}   name of the package in which the new class/interface is created
${USER}   current user system login name
${DATE}   current system date
${TIME}   current system time
${YEAR}   current year
${MONTH}   current month
${DAY}   current day of the month
${HOUR}   current hour
${MINUTE}   current minute