Wisdom teeth are the last molars to arrive, usually in the late teens or early twenties. When there is enough room and they come in straight, they can stay. Problems begin when they are impacted, sideways, or only partly emerged.
Signs that removal may be needed include recurring pain, swelling, food trapping, or crowding of nearby teeth. A simple x-ray shows the position clearly, so your dentist can recommend monitoring or a straightforward extraction.