Sexually transmitted diseases (STDs) are infections that are passed from one person to another through sexual contact. STDs can be caused by bacteria, viruses, or parasites, and can lead to a variety of health problems, including infertility and death. Common STDs include chlamydia, gonorrhea, syphilis, HIV, and genital herpes. Chlamydia is the most common of these and is caused by bacteria, while other STDs, such as HIV and genital herpes, are caused by viruses. Treatment for STDs vary depending on the type of infection, and some can be cured with antibiotics, while others can only be managed with antiviral medications. It is important to practice safe sex and get tested regularly to protect yourself and your partners from STDs.