"Sex-on-IMVU" refers to a category of pornographic content that takes place in the virtual world of IMVU, which is an online social gaming and chat platform. Users can create customizable avatars and interact with others through text, voice, or video chats. The tag specifically indicates sexual activities that occur within this virtual environment. It suggests explicit content involving avatars engaging in various sexual acts, such as intercourse, oral sex, or other intimate behaviors. This category of pornography is intended for adult audiences who enjoy virtual simulations and role-playing scenarios