These terms are not so much about sex, but about a consequence of sex called babies.
In man-on-man-sex terms a 'bottom' is the receptive partner in penetrative anal sex, and the 'top' is the penetrator. Because being a bottom is a unique and vastly varying experience, there are further terms that detail some more specific branches of bottom.
Vaginal containment is often used as a step in sex therapies, as a way of gradually introducing penetrative intercourse.
Vaginal dilators are smooth, rigid, cylindrical plastic shapes of varying sizes that are used to gradually stretch and lengthen the vaginal muscles.
Vaginal dilators can be really effective in the treatment of a number of medical conditions and are also used after gender reassignment surgery to help the healing process and prevent damage to the newly-formed vagina.
Medical conditions that can be treated with vaginal dilators include Vaginismus (vaginal muscle spasm and pain), Vaginal Agenesis (rare birth defect where the vagina is not fully formed), Lichen Sclerosus (genital scarring) , and damage to the vagina caused by radiation/ radiotherapy treatments.
A devastating birth defect where by the vagina fails to fully develop.
Vaginal Agenesis occurs when the muscular (vaginal) canal connecting the cervix and vulva stops developing due to the vaginal plate failing to form.
The disorder can result in a shorter vagina, or the complete lack of a vagina, and a small or even absent uterus. External genitalia appear normal, so the disorder is often not diagnosed until the sufferer reaches puberty and fails to start menstruating.
Sex is painful and in some cases impossible for women with Vaginal Agenesis. There are treatments (such as self-dilation) and surgical interventions (vaginoplasty) that can result in the development a healthy, normal sex life.
However many women with the disorder can't get pregnant, even after treatment, because of developmental abnormalities of the uterus, ovaries and fallopian tubes.