This document discusses sexual transmission diseases, also known as sexually transmitted infections (STIs). It notes that there are millions of new STI cases each year globally that are transmitted through sexual behaviors like vaginal, anal, and oral sex. It provides details on some of the most common STIs like chlamydia, herpes, HPV, gonorrhea, syphilis, and HIV/AIDS, noting their causes and potential complications if left untreated. The document stresses that prevention through safe sex practices is important to reduce the transmission of STIs.