Vaginal bleeding refers to any bleeding that occurs from the vagina, outside of a woman's normal menstrual period. There are many possible causes of vaginal bleeding, including:

1. Menstrual irregularities: including heavy or prolonged periods, irregular cycles, and missed periods.

2. Pregnancy: including ectopic pregnancy, miscarriage, and preterm labor.

3. Infections: including vaginal and cervical infections.

4. Hormonal imbalances: including hormonal changes during menopause or thyroid disorders.

5. Structural issues: including uterine fibroids, polyps, and endometrial hyperplasia.

6. Cancer: including cervical, endometrial, and ovarian cancer.

It is important to seek medical attention if you experience vaginal bleeding, especially if it is heavy, prolonged, or accompanied by other symptoms such as pain or discharge. A doctor can help determine the underlying cause and provide appropriate treatment.

Note: This is a general description. Please take professional health advice.