What is the difference between a colostomy and an ileostomy?
Both bring a piece of bowel to the surface as a stoma, but they use a different part of the gut, so the output differs. A colostomy uses the colon (large bowel), usually on the left side, and the stool tends to be firmer and less frequent, much like before. An ileostomy uses the end of the small bowel (ileum), usually on the right side, and the output is looser, more liquid, and more constant because the colon that normally absorbs water is bypassed. That bypass is why people with an ileostomy need to pay more attention to fluids, while firmer colostomy output can sometimes lean toward constipation.
This answer differs for an ileostomy and a colostomy.
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Both a colostomy and an ileostomy bring a piece of bowel to the surface of your tummy as a stoma, and both collect waste in a bag instead of passing it the usual way. The difference is which part of the bowel is used, and that one detail shapes almost everything else, from where the stoma sits to how the output looks and how often you empty the bag.
Ileostomy
An ileostomy uses the end of the small bowel, the ileum. It is usually placed on the lower right side of the abdomen. Because the small bowel feeds it directly, the output is looser and more liquid: the NHS describes the poo in the bag as "liquid or soft, like porridge" (NHS). It also tends to be more constant, so the bag is a drainable type emptied several times a day.
The colon normally reclaims water and salts from waste, and an ileostomy bypasses it. That is why hydration matters more here. The American Cancer Society notes that when the colon is removed you are "at greater risk for electrolyte imbalance" and advises drinking enough fluid, around 8 to 10 glasses a day, to avoid dehydration (American Cancer Society). Your stoma nurse can help you spot the early signs and set a fluid plan.
Colostomy
A colostomy uses the colon, the large bowel, and is most often placed on the left side. Because waste has already travelled through most of the colon, the output is firmer and closer to ordinary stool. Cleveland Clinic explains that stool from a sigmoid colostomy, the most common type, "is typically more solid than other types of colostomies" (Cleveland Clinic). It also tends to come less often, sometimes once or a few times a day.
The trade-off runs the other way: with firmer output, a colostomy can occasionally lean toward constipation rather than dehydration, so fluids and a steady routine still matter (Cleveland Clinic).
The short version
Same idea, different plumbing. An ileostomy means looser, more frequent output and a closer eye on fluids; a colostomy means firmer, less frequent output with constipation as the thing to watch. Which one you have depends on why surgery was needed and how much bowel is involved.