Chlamydia is a common sexually transmitted infection caused by the bacterium Chlamydia trachomatis. It often goes unnoticed as many people don't experience any symptoms, but if left untreated, it can lead to serious health complications. Common symptoms include pain during sex, abnormal discharge, and pain in the lower abdomen. The good news is that Chlamydia can be easily treated with antibiotics, usually clearing up within a week or two. Remember, the best way to prevent Chlamydia is to practice safe sex by using condoms and getting regularly tested.