Cervical Intraepithelial Neoplasia (CIN) refers to the presence of abnormal cell growth on the surface of the cervix. CIN is not cancer, but it can progress to cervical cancer if left untreated. It is usually detected through Pap smears and confirmed with a biopsy. CIN is categorized into grades (CIN 1, 2, or 3) based on the extent and severity of abnormal cells.