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 hue (its color can range from clear to a milky white-ish), depending on the time in your menstrual cycle. For example, there will be more discharge if you are ovulating, breastfeeding, or are sexually aroused. The smell may be different if you are pregnant or you haven't been diligent about your personal hygiene.
None of those changes is cause for alarm. However, if the color, smell, or consistency seems significantly unusual, especially if it accompanied by vaginal itching or burning, you could be noticing an infection or other condition.