Why do you go to the bathroom?

You go to the bathroom for several main reasons. First off, you need to relieve yourself by either urinating or having a bowel movement, so you can clean out your body of the toxins.
Some people also to the bathroom to vomit, again to remove toxins; but in that case them not being able to stomach something. Vomiting can sometimes occur from having an overly full stomach. It can also be the result of taking certain antacids.
To get rid of wastes that your body creates from food and drink.