Although cat communication has received little scientific study, purring ususally signifies contentment. It begins very early in the cat's life. The kitten's first purrs occur while feeding - and usually are in repsonse to or in concert with the mother's own purring. Often two cats will groom eanch other and purr. My cat loves to hide in paper bags and jump out at me.
Cats love to hide IN something, whether it's a drawer, a closet, or a bag.
They may just sit there and wait but usually peek and jump out as part of this behavior. There's much similarity in these actions to those of lions stalking their prey. Sometimes it will sit on my newspaper when I'm reading or on the desk on top of papers I'm writing. They like to be near people and often spend more of their time near their owners than dogs do. If they're perching on your paperwork, they're telling you they want attention.