A group of cats is called a clowder, a group of kittens is called a kendle.
All cats mark their territory with scent.
There are scent glands under the chin, so when a cat rubs against you with her head, she's marking you as part of her territory. A cat's sense of hearing is extremely acute and they can hear up to two octaves higher than humans. This enables her to catch her dinner. A cat will purr not only when happy, but when she's nervous. Less than one teaspoon of antifreeze can kill your cat, and they are attracted to its sweet taste.