What is an Ostomy?

The terms ostomy and stoma are general descriptive terms that are often used interchangeably, but they have different meanings.  An ostomy refers to the surgically created openings in the body for the discharge of body wastes.  A stoma is the actual end of the ureter (resulting in a urostomy) or small or large bowel (resulting in an ileostomy or colostomy, respectively) that can be seen protruding through the abdominal wall.

For a Colostomy, part of the colon (large intestine) is brought through an incision in the abdominal wall  and formed into a stoma (artificial opening) to allow the discharge of feces into a lightweight pouch.
Temporary Colostomy - performed to allow the lower portion of the colon to rest or heal. It may have one or two openings (if two, one will discharge only mucous). 
Permanent colostomy - usually involves the loss of part of the colon, most commonly the rectum. The end of the remaining portion of the colon is brought out to the abdominal wall to form the stoma.
The different types of colostomies are:
Descending colostomy: 
Opening is in the lower part of the large intestine. Discharge is semisolid. 
A loop colostomy:
Has one orient, but two tracts - the active, which discharges feces, and the inactive, which discharges mucous.
A double-barreled colostomy 
Has two openings.

For an Ileostomy, the ileum (lower part of the small intestine) is brought through an incision in the abdominal wall and formed into a stoma (artificial opening). Discharge, which is generally liquid or pasty, flows through the stoma into a lightweight pouch.

For a Urostomy, a stoma (artificial opening) is made in the abdominal wall  for the 
discharge of urine to bypass the bladder. There are different types of urostomies, depending on how the diversion is made.