Purrs, chirps, hisses and snarls…

What exactly is your cat trying to tell you?

A stray tabby gives birth to a litter of three kittens under the lilac bush in a backyard. As she nurses them, she purrs; as they suckle, the kittens purr, too. When the queen shifts her weight to try to find a more comfortable nursing position, one of the kittens lets out a distress call, indicating he's trapped under his mother's weight. She readjusts herself, and the purring party continues. One morning, the mother cat decides to move her litter to a safer spot. She deposits the first one inside the garden shed, and goes to retrieve the next one. Detecting the absence of his mother via his sense of smell, the kitten in the shed lets out a loud distress call, distinctly meant to reunite mothers and wayward kittens.As the kittens mature, the queen spends more time away from the nest, hunting for prey to ensure enough milk for her growing crew. Each time she returns, she gives out a "burp" to her kittens. When the kittens enter the weaning stage, the queen brings prey home to them, calling them over to it with a chirp. The kittens also begin to make chirping noises in anticipation for what they are about to receive. However, one night's dinner is interrupted when Mom lets out a long, low-pitched grow. The kittens scatter and retreat to safety inside the shed before the owl overhead can snatch one for his own evening meal.
As independent hunters, cats have limited need for an extensive vocal repertory. Cat-to-cat vocalizations are generally limited to communicating with one's kittens, one's sexual partners and one's potential enemies. There is also an array of vocalizations used by our furry friends when they attempt to communicate with us.
By changing volume, intensity and number of repetitions of the vocalizations and backing them up with expressive body language and olfactory signaling, cats ensure their messages are received and that their needs are met.
Purring 101The purr is the most common sound issued by cats—and yet one of the least understood. Kittens just a few hours old begin purring as they knead their mother’s chest and nurse. The purr sound is made both on the inhale and the exhale, with an instantaneous break between breaths. Built-up pressure created by the opening and closing of the glottis results in a sudden separation of the vocal folds, creating the purr. While purring is often heard when the cat seems content, those familiar with handling cats in pain or near death know that they also purr when under duress, the reason for which is yet unknown.
The Meaning of MeowThe second most common vocalization is the meow. Rarely heard between cats, this vocalization seems tailor-made for communication between cats and humans. Early on, cats notice that meowing brings attention, contact, food and play from their human companions. Some behaviorists suggest that certain cats seem to alter their meows to suit different purposes, and that some guardians can differentiate between, say, the “I’m Hungry!” meow” from the "Let Me Out!" meow.
The meow is the most often used of the vowel patterns—vocalizations produced with the mouth first open and then gradually closing. - The sound cats make when highly aroused by the sight of prey is called chirping. - When a cat is frustrated (such as when an indoor cat finds he is unable to get to the birds at the feeder), you may hear him chatter. - When a neonate kitten is cold, isolated from his mother or trapped, he issues a distress call—also sometimes called an anger wail. As the kitten matures, the distress call is used when play is too rough or the cat finds something else to protest.
A Hiss Is Just a Hiss?All threat vocalizations are produced with the mouth held open. These sounds mirror the cat's intense emotional state. A hiss is uttered when a cat is surprised by an enemy. A high-pitched shriek or scream is expressed when the cat is in pain or fearful and aggressive. Snarling is often heard when two toms are in the midst of a fight over territory or female attention. And a long, low-pitched growl warns of danger.

Source: ASPCA