Vaginal yeast infections also called candidiasis is an infection caused due to the changes in the vaginal bacterial and yeast count. Some of the symptoms of a yeast infection include itching, swelling, thick thick discharge and irritation. Yeast infections are easily treatable. They are considered an STI but sexual contact can worsen the infection.
Sources:
https://www.mayoclinic.org/diseases-conditions/yeast-infection/symptoms-causes/syc-20378999
https://www.webmd.com/women/guide/understanding-vaginal-yeast-infection-basics
https://my.clevelandclinic.org/health/diseases/5019-yeast-infections
https://www.healthline.com/health/vaginal-yeast-infection#symptoms