This is a built-in template used by IDEA each time you create a new Java class, by selecting New | Class from the popup menu in one of the project views.
The template is editable. Along with Java expressions 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 tamplate as a parameter in quotation marks.
Predefined variables will take the following values:
${PACKAGE_NAME}   name of the package in which the new class is created
${NAME}   name of the new class specified by you in the New Class dialog
${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