In 1976, the World Health Organization referred to diseases transmitted through sexual intercourse or similar acts collectively as sexually transmitted diseases (STDs). It was later discovered that some infections do not present with signs and symptoms, but merely carry the pathogen, but can act as an infectious agent causing transmission, hence the concept of sexually transmitted infections (STI) was proposed to express this. The only five “classical STIs” are syphilis, gonorrhea, soft chancre, lymphogranuloma venereum, and inguinal granuloma. In addition to the above five “classical STDs”, sexually transmitted diseases involve almost the entire range of medical microorganisms. The main diseases include: 1) bacterial diseases: syphilis, gonorrhea, soft chancre, inguinal granuloma, etc.; 2) viral diseases: AIDS, genital herpes, condyloma acuminata, etc.; 3) fungal diseases: genital candidiasis, etc.; 4) chlamydial diseases: venereal granuloma; 5) insect diseases: trichomoniasis, scabies, pubic lice, etc. It should be emphasized that some of the above diseases are not necessarily transmitted through sexual or similar sexual acts, and thus should be treated differently depending on the mode of transmission to avoid unnecessary personal, family and social conflicts.