An intrauterine device (IUD) is a small device made from plastic and copper which sits inside the womb (uterus). It is also known as "the coil". Two threads are attached to the IUD and pass out through the neck of the womb (cervix) to lie in the vagina. These allow the IUD to be removed easily. Most devices are T-shaped (the two arms of the T fold flat for insertion) and are about as long as a matchstick. The inside of the womb itself is only a little longer than a matchstick, so the device sits neatly inside.
This is a companion discussion topic for the original article at https://patient.info/sexual-health/long-acting-reversible-contraceptives-larc/intrauterine-contraceptive-device