PID is an infection of the female reproductive organs, often caused by sexually transmitted bacteria that spread from the vagina to the uterus, fallopian tubes, or ovaries. Symptoms may include pelvic pain, fever, abnormal discharge, and pain during intercourse. If untreated, PID can lead to infertility, chronic pain, and ectopic pregnancy. Prompt antibiotic treatment is essential, and severe cases may require hospitalization.