Cat communication methods:
1. Scent communication. Cats use scent to mark their territory and also to mark their companions. For example, they might rub their head against another cat or rub their tail against another cat's body; this is how cats use their glands to mark their territory with scent.
2. Physical contact. Cats that have a good relationship will have more physical contact, such as grooming each other, huddling together to sunbathe, or rubbing their tails against each other. In the cat world, only cats of a higher status will groom other cats.
3. Vocal communication. Cats communicate with humans by meowing, but cats do not communicate with each other by meowing. Cats only make sounds when they are aggressive or fighting. Different sounds, loudness, and pitch can effectively express a cat's emotions. 
How cats communicate with humans:
1. Purring. A cat's purring may indicate that it is content, but it is more likely to indicate that it is scared, sick, or injured and wants you to offer it some help.
2. Meowing. Meowing is the most common way cats communicate with humans, and it's also what they consider the most effective way to communicate.
3. Tail posture. A loose, upright tail indicates a happy cat, while a tail with the same upright fur suggests anger or fear. A low-set tail means your cat is anxious or insecure.
4. Blinking. When you're with your cat, slow blinking means he's comfortable around you.
5. Halloween Pose. When your cat or anything else feels threatened, it will strike a classic cat pose with an arched back, a high tail, and upright hair.
6. Rubbing against you. Rubbing against your legs is how your cat marks your territory, and can also be interpreted as your cat showing you that it loves you.
