The bowel is a long tube that carries food from the stomach to the rectum. Along the way, food is digested and nutrients are absorbed. Fluid is absorbed in the lower part of the bowel, known as the colon. The residue from undigested food forms the bowel motions (faeces) and passes into the rectum.
The anal sphincter at the end of the rectum keeps the back passage closed and prevents the faeces from leaking out. When the rectum is full, nerve endings in the rectum send signals to your brain to tell you that you need to pass a bowel motion. When you go to the toilet, the rectum squeezes the motion out through the anus.
Your bowel motions should be soft and easy to pass, and you should not need to strain. Different people have different bowel habits, so your bowel motions may come several times a day or once every two or three days.