Vagina normally produces secretion to maintain lubrication and protect the inside wall. It is normally clear or slightly white in colour.
When there is infection such as Gonorrhea and Chlamydia, the secretion becomes coloured and thinker. It may be itching and has an odour. It becomes "discharge".
Leukorrhea is a mild, odourless discharge from the vagina that is clear or milky in colour. It is a made up of the cells from the mucus membrane in the vagina, glandular cells and endometrium cells in the uterus. The volume of secretion varies through menstrual cycle and at different ages (during and after pregnancy or during or after menopause). It is also affected by sexual stimulation.
Thus, if you see clear and odourless discharge in your underwear, don’t worry; it is normal. If your vaginal discharge carries odour or is yellow or green in colour, or becomes cheese like in texture, then you may be experiencing an infection. It's time to seek medical attention. Do not self-medicate!