Group on facebook

Hi im kind of confused and dont know what to do, my boyfriend is on a group chat called lamp lovers, all iv saw of it is a glimpse and its basically half naked or naked girls next to lamps all the time and i dont know whether him and his mates are in it as a laugh or what, have any of you heard of anything like this and what it is and should i be worried. I dont mind him watching porn so if it is just something like that i wouldnt know what to say however if it was to date people etc please can someone help me out on what to do/say to him (im trying to make it as short as possible so i will reply with more answers) xx