A yeast infection (candidiasis) happens when a fungus that already lives naturally in the vagina overgrows, causing itching and a white discharge (similar to cottage cheese). It is not a serious disease or "dirty", it's just an imbalance that can happen due to heat, tight clothes, or stress. If you feel these symptoms, don't despair: talk to an adult and go to the gynecologist. With a simple cream or medicine, everything goes back to normal quickly!