Use the word entrails when you want to refer — in a not too gory way — to the internal organs of a person or animal, particularly a dead one.
If the inner parts of an animal are exposed, you can call them its entrails. The organs, particularly the intestines, are collectively known as an animal's entrails, and it's more common to refer to them this way if they're visible or removed from the body. Sometimes the noun entrails is used to mean the inside of something else, like the entrails of a street that's been dug up and exposed. The Latin interanea, or "internal," is the root of entrails.