Vaginal discharge serves an important housekeeping function in the female reproductive system. Fluid made by glands inside the vagina and cervix carries away dead cells and bacteria. This keeps the vagina clean and helps prevent infection.
Most of the time, vaginal discharge is perfectly normal. The amount can vary, as can odor and color (which can range from clear to a milky white-ish), depending on the time in your menstrual cycle. For example, there will be more discharge when you're ovulating, breastfeeding, or sexually aroused. It may smell different when you're pregnant or you've been letting your personal hygiene slide.
None of those changes is cause for alarm. However, if the color, smell, or consistency seems quite different than usual, especially if you also have vaginal itching or burning, you could be dealing with an infection or other condition.