a hermie or hermaphrodite has male and female flowers. the male flowers will pollinate the females in the garden, this will give you seeds instead of bud. usually this occurs as a few male flowers on a predominately female plant and will give you some seeds but not completely devastate your harvest, but it can happen. if you have a hermie cutting it down would depend on some other factors such as what caused it to pop some male flowers, how many plants you have and how many male flowers you are getting.
in my experience i usually get around 60-70% females although i have had under 50% in the past. if your using bag seed it is most likely you will get female or hermie as the seeds will be most likely made from a stray male flower on a hermie