What does the Self Clean+ function do and when should I use it?

Self Clean+ is a self-cleaning cycle that removes mold that may occur inside the washing machine without using detergent or bleach. Regular use after every 40 washes is recommended. To use it, press Power, then press Self Clean+, then press Start/Pause. Never use Self Clean+ when laundry is in the machine as it may cause damage. (Page 31)