Varies. Many times, STDs such as chlamydia can be completely asymptomatic. One would never know they had it unless they got tested at their doctor's office. Other STDs show signs such as sores on the genitals or pain during sex or urination. If you think you have an std, you might consider seeing your physician for some tests.
Varies. Sexually transmitted infections can cause various genital lesions. These lesions may be painful or painless, ulcer or flat or bumpy. They may be itchy. The genitals may discharge various fluids. This link will give you an idea of all the variations. These are sensitive medical images. The site also gives a good warning about the content. Http://www. Avert. Org/std-pictures. Htm.