The commonest would be "thrush" a fungal infection.
"Thrush" is commonly known as a yeast infection which is also described above which you can get with or without sexual transmission.
The most commonly transmitted STD is Chlamydia.
Sexually transmitted diseases (STDs) may cause UTI (Urinary Tract Infections) -like symptoms, such as pain with urination. This is due to the inflammation and irritation of the urethra or vagina that's sometimes associated with chlamydia and other STDs. If untreated, STDs may lead to serious long-term problems, including pelvic inflammatory disease (PID) and infertility. Unlike UTIs, STDs are contagious.