A size queen is a person who prefers to have sex with people with big penises, whether that entails oral, vaginal or anal sex. It is also occasionally used to refer to people who like big sex toys as well. A size queen can be of any gender; however, the term is believed to have originated in the gay community. Regardless of a size queen's gender, size does matter in terms of the level of attraction they feel for and the pleasure they receive from a partner.
Although there is cultural fear around large penises (and sex toys) and the idea that they can permanently "stretch out" the vagina or anus, this is simply not true. The skin and muscle is elastic and returns to its normal size. That said, taking on a larger-sized penis may require going slower and using more lube. For anal play with a larger penis or sex toy, anal training is often used to make this possible by helping the muscles learn to relax and stretch farther.