Why do cats have whiskers?
The Real Answer
Cats have whiskers because whiskers are specialized sensory hairs that give them detailed information about things close to their face. The whisker itself is just hair, but movement of that hair is transmitted to sensory receptors in the follicle at its base.
When a whisker bends against an object or is disturbed by nearby movement, the cat's nervous system gets tactile information it can use to judge nearby surfaces, openings, and obstacles. That is especially useful at close range, where whiskers supplement the cat's other senses.
Whiskers are therefore not just decorative facial hair, and they are not a separate balance organ. They are part of a highly sensitive touch system around the face and other whiskered areas.
You spend all day being told not to mess with a cat's whiskers, then at 3 a.m. the cat pushes them across your face because breakfast is late. You stay completely still until one whisker finds your nostril, then get out of bed and reward the technique.
Why People Ask This
People ask because whiskers look like ordinary long hairs but cats seem to treat them differently from the rest of their fur. The useful clue is that whiskers are connected to a specialized sensory system, so a small bend in the hair can carry information about what is happening immediately around the cat's face.