It’s happy because the more you rub it, the more it owns you.
Cats have scent glands for marking their territory on their cheeks and chins:
Temporal Glands
There are two glands, one at each temple, that cats use to rub their scent on items they are claiming. This is why they headbutt and rub objects. They also use these scent glands to keep markers of their location so they can easily find their way back home. The areas on the head where fur is finer is where the glands are and the skin is often slightly oily.
Cheek Glands
There are two, one on each cheek, that cats use the same way they use their Temporal Glands. However, these scent glands produce fewer oils and coat the whiskers to rub the oil against objects easier.
