This is commonly called a "yeast" infection.
It is usually caused by Candidia albicans which is a fungus normally found in small amounts in the vagina.
The most common symptoms of a yeast infection are itching and burning of the vulva, which sometimes results in redness and swelling of this area, making sex and urination painful. Vaginal discharge from yeast is sometimes described as "cottage cheese-like" because of its white and lumpy texture. There may be a "yeasty" odor.
Man, that chick I did last week had Vulvovaginal Candidiasis so bad... it looked like she was baking a loaf of bread! But, I ate it anyway!