Purring: Cats make the purring sound whey they are happy. Purring is also used to put themselves at ease. Purrs are typically a sign the cat is content. Most cats purr when they are happy and being petted, loved and adored. Purring can also be a self comforting mannerism, like a small child would such their thumb for instance.
Chirping: Cats chirping can indicate they are looking for attention. Petting your cat after hearing them chirp will reinforce them.
Meowing: Cats communicate using many types of meows. Meowing is generally a cat to human interaction, although kittens will use meowing to communicate with their momma. Meows are generally calls for attention, especially the short meows. Meows with an increased duration can convey a sense of urgency, we often hear this when a cat is requesting to be fed. Prolonged meows also indicate distress, especially when they pair it with restless pacing back and forth.
Growling: Growling is generally used as a warning signal and generally precedes hissing. It is a cats way of communicating the cats displeasure with the immediate happenings and surroundings. Usually a growl doesn't mean an immediate attack, but may be the case, so be careful when a cat starts growling.
Chattering: When a cat chatters, they are showing that they are getting ready to attack its prey. When a cat chatters they are showing excitement and/or frustration. When bird watching through a window at a bird outside we have noticed our cats chirping as if to say, "help me get that!" Chattering is thought to calm the prey into a false sense of security so the cat can approach it prey more closely before striking.
Hissing: If your cat arches its back and spits, it is recommended you keep your distance. When a cat spits or hisses, it's letting you know that it's frightened or angry. A cat hisses and spits when it feels threatened by a person, animal or situation and it is it's way of attempting to scare the aggressor off. If hissing does not work, an attack by the cat generally follows.