A 2D ultrasound is a type of medical imaging technique that uses sound waves to produce images of the inside of the body. In the context of gynecology, it is primarily used to visualize the female reproductive organs, including the uterus, ovaries, and fallopian tubes. The "2D" refers to the two-dimensional, black-and-white images produced by this method, which provide a flat, cross-sectional view of the anatomy.