Scratching is an important and complex part of life as a cat. Many owners have the misconception that scratching is merely the cat's attempt to sharpen his claws or that the behavior is rooted in some spiteful attempt to deliberately misbehave. In truth, scratching serves many purposes. Scratching is actually more akin to grooming than sharpening, as the purpose is often to shed old claw sheaths from the front claws (cats usually chew the sheaths from their back claws).
2. Marking area Cats tend to pick a small number of conspicuous objects in their environments to scratch such as trees, fence posts, the corner of the couch, etc., and return to them repeatedly. The scratched surface leaves a highly visible mark that can be easily seen by other cats. In addition, cats have scent glands in their paws so that when they make scratching movements they leave odor cues that the cats can smell. The fact that cats leave scent marks by making scratching movements may be the reason that cats will continue to try to scratch objects. Marks left by clawing also let other cats know by sight who owns a given object or area.
3. Muscle strain Cats also claw to comfort themselves during times of fear or stress. Single cats may never or rarely scratch, and then become scratch-maniacs when more cats enter the home. Clawing also feels good. It provides great aerobic exercise to stretch the shoulder and foreleg muscles, and keeps nails healthy. Read more http://adf.ly/9KYx
You might also like:
What is the purpose of a cat scratcher post
Choosing an appropriate scratching post
How to train your cat scratches on a scratches post