Dog diapers are made explicitly for canines. There are several types of diapers, but the reusable and disposable ones are the most popular. While disposable diapers are easier to use as you can toss them away, reusable ones are better in the long term.
The main reason your pup needs to wear a diaper is potty training, but they might need to wear them due to health problems too. If you have a female dog that's not neutered, she will need to wear a diaper while in heat.