In most cases, cats will purr when they are in a relaxed environment, sending out waves of calmness. This may also occur when you stroke them, and if this is the case, your feline friend is feeling happy or sociable. However, cats purr to communicate other emotions and needs, too.
What does it mean when a cat is purring?
Purring (and many other low-frequency vocalizations in mammals) often are associated with positive social situations: nursing, grooming, relaxing, being friendly. More likely, though, purring is simply soothing, or self-soothing, as cats may also purr in stressful situations.
Do cats have control over their purr?
Even cooler: Your cat does not control the signals from her central nervous system that tell her to purr, meaning she has the best autopilot setting known to humanity.