The term "ventral side" refers to the underside or belly of an organism. In animals, this is the surface that typically faces the ground when they are in a natural position. For example, in humans and many other mammals, the ventral side includes the chest and abdomen. In contrast, the opposite side is known as the "dorsal side," which is the back. Understanding the ventral side is important in fields like anatomy and biology, as it helps in identifying the orientation and structure of various organisms, including fish, birds, and mammals.