Sexually transmitted infections, or STIs, are infections that are primarily spread through sexual contact. They can be caused by bacteria, viruses, or parasites and can affect anyone who is sexually active. Common STIs include chlamydia, gonorrhea, syphilis, and HIV. Many people with STIs may not show symptoms, making regular testing important for sexually active individuals. Preventing STIs involves practicing safe sex, such as using condoms and having open conversations with partners about sexual health. Getting vaccinated against certain STIs, like human papillomavirus (HPV), can also help reduce the risk. Early detection and treatment are crucial for maintaining health and preventing complications.