The term "man cave" is a metaphor describing a room where one or more male family members and optionally their family and their friends are supposed to be able to do as they please, without fear of upsetting any female household members with their interior design choices. It's somewhere where the entire family can switch off.

After a hard day at work, what best to take five minutes and chill in your Man Cave. Be it alone, with your family or with friends. 

It's where you get dropped off to to relax. 

Here you will find some indulgent and selfish things.