Use this window to create sub categories/periods which can exist within 
absence groups and absence types. Absence periods are used in combination with 
functions defined in the  Absence Functions window so that the 
absence registered by an employee can be divided into sub periods.
E.g. Absence type SICK (sick leave) can 
be divided into sub periods such as PAID, UNPAID etc. When an employee registers 
an absence period using the absence type SICK, the absence period will be 
proportioned among the sub periods PAID and UNPAID depending on the link between 
absence functions and the absence periods.