Amazingly enough, meowing is one of the rare forms of communication that cats reserve exclusively for humans. With the exception of young kittens, who meow when they are hungry, cats do not meow to other cats.
As anyone with a chatty kitty knows, meowing can occur in a wide range of pitches and volumes. Cats meow as a form of greeting, a way to ask for attention, or to get their food bowl topped off. Older cats suffering from cognitive impairment may meow when they are disoriented. Certain breeds, such as Siamese, are known for high amounts of meowing behavior.