A hairball is a ball of undigested hair stuck in the stomach or small intestine of a cat.
Digestion in cats is often complicated by the ingestion of large amounts of hair during grooming. Cats will eliminate hairballs often through retching or vomiting them out.
Cats develop hairballs when they groom themselves by licking.
Cat's tongues have rough surfaces made of backward slanting papillae. Much of the hair can't be dislodged, and the cat is unable to spit it out. And as a result, loose fur is swallowed. Majority of this hair passes all the way through the digestive tract, but if some hair stays in the stomach it can form a hairball. Eventually the cat will vomit to get rid of the hairball.
While hairballs are often normal occurrences, they can still be potentially dangerous. If the hairball becomes large or dense enough, it may block the intestinal tract so that the cat is unable to hack or vomit it out. If this occurs, it may need to be removed by surgical means. Most hairball instances can be prevented by feeding your cat hairball product or laxative that helps eliminate hairballs through natural means.
Cats are always grooming themselves; your cat would love and appreciate if you would brush them to remove any loose hair. Brushing or combing is the easiest way to reduce hair ingestion, and it also helps keep it off your furniture. Another preventive method is to include a Hairball product or laxative in their diet, some pet food come with a hairball reduction formula with high fiber content. These not only encourage hairballs to pass through the digestive tract, but also minimize shedding and keep your cat's coat healthy.
LaxaCat Hairball Remedy Cat Lax (2 oz) Calm Coat Hairball Treats for Cats

FURminator Long-Hair deShedding Tool for SMALL Cats Millers Forge Vista Cat Brush Bamboo Cat Rotating Fine Tooth Comb