Cats' tongues are bristly and sandpapery because they use their tongues to clean and groom their fur. The rough surface brushes the fur, sort of like a hairbrush, and helps remove the loose, dead hairs.

cats have tongues to ball up there chewed food and to force there food down the throught.

Cats have well developed papillae; this is why their tongues feel like sandpaper when they try to groom you.

Cats use their tongues to help them eat and drink. They do not sip water as humans do, they lap it up with their tongues. Watch them some time.

You can make and find them in dogs tongues and cats tongues.