The sigmoid colon is a part of the large intestine located just before the rectum. It is shaped like an "S" and connects the descending colon to the rectum. Its primary function is to store fecal waste until it is ready to be expelled from the body. This section of the colon plays a crucial role in the digestive process by absorbing water and electrolytes from the waste material. The sigmoid colon also helps regulate bowel movements, making it an important component of the gastrointestinal tract.