Sexually Transmitted Diseases are simply known as STDs. An STD is an infection that is passed from one person to another during sexual activity. Body fluids and secretions are exchanged during intimate sexual contact. The exchange occurs not only during vaginal intercourse but also during other activities, such as oral sex and “outercourse.” The most common way to become infected with an STD is through vaginal intercourse. However, intimate sexual contact can transmit infections.