I-Pill 1.5 is an emergency contraceptive tablet containing 1.5mg of levonorgestrel, a synthetic progestin that prevents pregnancy when taken within 72 hours (3 days) after unprotected sex or contraceptive failure, though it's most effective when taken as soon as possible. It works primarily by preventing or delaying ovulation and may also alter the uterine lining to prevent implantation, but it cannot terminate an existing pregnancy and is not meant for regular contraceptive use.