While self-grooming, cats often come upon dead hair. Ingested hair usually travels along the cat's digestive system and gets excreted in the feces. The problem occurs when the cat swallows too much hair and can't pass it along the usual route. In that case the hair accumulates in the stomach and forms a wad of compressed hairs. The cat finally vomits the mass of hair, making quite a spectacle of coughing and retching.
Any cat can suffer from an occasional hairball, but some cats are more susceptible than others.
Generally speaking, longhaired cats tend to swallow more hair mass, simply because they have more of it. The density and length of the cat's fur are thus a factor. The major problem that hairballs can create is intestinal blockage. Sometimes, the cat can neither pass the hair in the stool, nor vomit up the hairball. The hairball remains in the cat's intestines, partially or even totally blocking them.