Sexually transmitted infections (STIs) are infections that can be passed on from one person to another through sexual contact. STIs are also known as sexually transmitted diseases (STDs). The most common STIs are chlamydia, gonorrhea, syphilis, genital warts, and HIV/AIDS. Chlamydia is a bacterial infection that can cause pain in the lower abdomen, discharge from the penis or vagina, burning during urination, and pain during sexual intercourse. It can be treated with antibiotics. Gonorrhea is a bacterial infection that can cause burning during urination, unusual discharge from the penis or vagina, and pain during sexual intercourse. It can be treated with antibiotics. Syphilis is a bacterial infection that can cause a sore on the genitals, fever, headache, and swollen lymph nodes. It can be treated with antibiotics. Genital warts are caused by a virus and can cause itching, burning, and pain. Genital warts can be treated through topical creams. HIV/AIDS is caused by the Human Immunodeficiency Virus (HIV). It can be spread through sexual contact, sharing needles, and from mother to child during pregnancy and birth. To reduce the risk of HIV transmission, it is important to use condoms and practice safe sex. STIs can be prevented by using condoms, avoiding sexual contact with multiple partners, and getting tested regularly. It is also important to practice safe sex and talk to partners before engaging in sexual activity.