Expert suggests that cats are so complex that they communicate with you, other felines and other animals in very unique ways. Of course, in addition to their vocalization skills, they also communicate through a broad range of body postures as well. These are often easier to interpret than their meows are.
Nearly everyone who has had the privilege of hearing a cat purr knows that it generally translates to something good. However, contrary to what you may have been taught to believe, purrs are not always positive. This sounds that warms your heart is made when the feline breathes in and out with quick pauses occurring between breaths. The purr is created by a separation in the vocal folds caused by built up pressure. It is actually a very complex process and you should feel special if a cat directs this type of communication in your direction.
Although purring is typically perceived as a sign of happiness or contentment, cats in pain will often purr when they are stressed as well, an act that remains a mystery.
It's no secret that hissing is a warning that you should take seriously; cat bites are not fun to deal with. (If you want to correct your cat's biting behavior, here's an excellent resource: http://catbehaviorsolutions.com/Ebook/index.html)
There are different variations of hisses as well. If you startle or upset a cat, you will often be faced with a mouth open hiss. This is common if you invade their space.
If a cat is extremely distraught or fearful, a scream is often released along with the hiss. When you hear cats fighting outside and low-pitched angry growls are present, this is another form of hiss.
Now for the most confusing vocalization of them all; the meow! No one will ever know what every meow means but if you are really in tune with your feline friend, you'll begin to notice a pattern which will help you understand their needs.
Cats don't have only one generic meow. If you pay attention, you will discover that your cat will make a different sound for food, attention, boredom, if he wants outside, etc. Cats are highly intelligent creatures; they are trying to teach you what they want if you are observant. Just as humans train dogs through consistent repetition, cats train humans with their communication…not all people pick up on their daily lessons though.
It is also interesting to note that cats rarely meow to one another; meows are reserved for their human companions! If you take the time to really get to know your cat, you will learn what exactly they are asking for, when they're happy and when they are just plain frustrated.