Cats purr to communicate contentment when we pet them. They also purr when they are afraid or sick. Their purring helps to calm them and may have healing properties. Cats purr when approaching another cat in a friendly way, trying to make friends. Other reasons that cats purr for self-comfort when they are afraid, sick, or in some kind of distress, so purring is not always an indication that all is well.
Among other diverse sounds that cats make are meowing and chattering. Many cats meow at you for food and for attention. Many Siamese will “talk” to you more than you might like. A few of my cats also do a great deal of chattering, especially when they are excited about seeing those critters and birds while doing some kitty window shopping in the living room. Chattering is a behavior that cats have in the wild that imitates the sounds that their prey make. These sounds can be used to trick the prey into being caught.