An entry wound is the hole made by an object penetrating the skin. The thing to remember is that an exit wound must have a corresponding entry wound, but sometimes an object can enter the body but not leave, as in the case of someone getting shot in the temple with a .22, the small, light bullet will bounce around inside the crainium and turn the brain into applesauce, but will most likely not punch back out. If anyone can think up a way to sustain an exit wound without an entry first, please let me know.