Cats stick their butt in your face as a gesture of friendship.
Cats head butt as a way to deposit their pheremones onto people or objects. This is a way to mark something as safe.
Cats yawn as a way to end a confrontation with another animal.
Cats often attack ankles out of pure boredom.
Cats often sleep on things that smell like their owners. (Awe!) This can include pillows and dirty laundry. (Ew!)